diff --git a/platform/chromium/vapi-background.js b/platform/chromium/vapi-background.js
index 9413033f6..8e67b3d23 100644
--- a/platform/chromium/vapi-background.js
+++ b/platform/chromium/vapi-background.js
@@ -519,6 +519,62 @@ vAPI.messaging = {
 
 /******************************************************************************/
 
+// This allows to avoid creating a closure for every single message which
+// expects an answer. Having a closure created each time a message is processed
+// has been always bothering me. Another benefit of the implementation here
+// is to reuse the callback proxy object, so less memory churning.
+//
+// https://developers.google.com/speed/articles/optimizing-javascript
+// "Creating a closure is significantly slower then creating an inner
+//  function without a closure, and much slower than reusing a static
+//  function"
+//
+// http://hacksoflife.blogspot.ca/2015/01/the-four-horsemen-of-performance.html
+// "the dreaded 'uniformly slow code' case where every function takes 1%
+//  of CPU and you have to make one hundred separate performance optimizations
+//  to improve performance at all"
+//
+// http://jsperf.com/closure-no-closure/2
+
+var CallbackWrapper = function(port, request) {
+    // No need to bind every single time
+    this.callback = this.proxy.bind(this);
+    this.messaging = vAPI.messaging;
+    this.init(port, request);
+};
+
+CallbackWrapper.junkyard = [];
+
+CallbackWrapper.factory = function(port, request) {
+    var wrapper = CallbackWrapper.junkyard.pop();
+    if ( wrapper ) {
+        wrapper.init(port, request);
+        return wrapper;
+    }
+    return new CallbackWrapper(port, request);
+};
+
+CallbackWrapper.prototype.init = function(port, request) {
+    this.port = port;
+    this.request = request;
+};
+
+CallbackWrapper.prototype.proxy = function(response) {
+    // https://github.com/chrisaljoudi/uBlock/issues/383
+    if ( this.messaging.ports.hasOwnProperty(this.port.name) ) {
+        this.port.postMessage({
+            requestId: this.request.requestId,
+            channelName: this.request.channelName,
+            msg: response !== undefined ? response : null
+        });
+    }
+    // Mark for reuse
+    this.port = this.request = null;
+    CallbackWrapper.junkyard.push(this);
+};
+
+/******************************************************************************/
+
 vAPI.messaging.listen = function(listenerName, callback) {
     this.listeners[listenerName] = callback;
 };
@@ -605,58 +661,25 @@ vAPI.messaging.broadcast = function(message) {
 
 /******************************************************************************/
 
-// This allows to avoid creating a closure for every single message which
-// expects an answer. Having a closure created each time a message is processed
-// has been always bothering me. Another benefit of the implementation here
-// is to reuse the callback proxy object, so less memory churning.
-//
-// https://developers.google.com/speed/articles/optimizing-javascript
-// "Creating a closure is significantly slower then creating an inner
-//  function without a closure, and much slower than reusing a static
-//  function"
-//
-// http://hacksoflife.blogspot.ca/2015/01/the-four-horsemen-of-performance.html
-// "the dreaded 'uniformly slow code' case where every function takes 1%
-//  of CPU and you have to make one hundred separate performance optimizations
-//  to improve performance at all"
-//
-// http://jsperf.com/closure-no-closure/2
-
-var CallbackWrapper = function(port, request) {
-    // No need to bind every single time
-    this.callback = this.proxy.bind(this);
-    this.messaging = vAPI.messaging;
-    this.init(port, request);
-};
-
-CallbackWrapper.junkyard = [];
-
-CallbackWrapper.factory = function(port, request) {
-    var wrapper = CallbackWrapper.junkyard.pop();
-    if ( wrapper ) {
-        wrapper.init(port, request);
-        return wrapper;
-    }
-    return new CallbackWrapper(port, request);
-};
-
-CallbackWrapper.prototype.init = function(port, request) {
-    this.port = port;
-    this.request = request;
-};
-
-CallbackWrapper.prototype.proxy = function(response) {
-    // https://github.com/chrisaljoudi/uBlock/issues/383
-    if ( this.messaging.ports.hasOwnProperty(this.port.name) ) {
-        this.port.postMessage({
-            requestId: this.request.requestId,
-            channelName: this.request.channelName,
-            msg: response !== undefined ? response : null
+vAPI.messaging.send = function(tabId, channelName, message) {
+    var port;
+    var chromiumTabId = toChromiumTabId(tabId);
+    for ( var portName in this.ports ) {
+        if ( this.ports.hasOwnProperty(portName) === false ) {
+            continue;
+        }
+        port = this.ports[portName];
+        if ( chromiumTabId !== 0 && port.sender.tab.id !== chromiumTabId ) {
+            continue;
+        }
+        port.postMessage({
+            channelName: channelName,
+            msg: message
         });
+        if ( chromiumTabId !== 0 ) {
+            break;
+        }
     }
-    // Mark for reuse
-    this.port = this.request = null;
-    CallbackWrapper.junkyard.push(this);
 };
 
 /******************************************************************************/
diff --git a/platform/chromium/vapi-client.js b/platform/chromium/vapi-client.js
index de7147293..5d62a5fd8 100644
--- a/platform/chromium/vapi-client.js
+++ b/platform/chromium/vapi-client.js
@@ -73,49 +73,148 @@ vAPI.shutdown = (function() {
 
 /******************************************************************************/
 
+var MessagingListeners = function(callback) {
+    this.listeners = [];
+    if ( typeof callback === 'function' ) {
+        this.listeners.push(callback);
+    }
+};
+
+MessagingListeners.prototype.add = function(callback) {
+    if ( typeof callback !== 'function' ) {
+        return;
+    }
+    if ( this.listeners.indexOf(callback) !== -1 ) {
+        throw new Error('Duplicate listener.');
+    }
+    this.listeners.push(callback);
+};
+
+MessagingListeners.prototype.remove = function(callback) {
+    if ( typeof callback !== 'function' ) {
+        return;
+    }
+    if ( this.listeners.indexOf(callback) === -1 ) {
+        throw new Error('Listener not found.');
+    }
+    this.listeners.splice(this.listeners.indexOf(callback), 1);
+};
+
+MessagingListeners.prototype.process = function(msg) {
+    var listeners = this.listeners;
+    var n = listeners.length;
+    for ( var i = 0; i < n; i++ ) {
+        listeners[i](msg);
+    }
+};
+
+/******************************************************************************/
+
 var messagingConnector = function(response) {
     if ( !response ) {
         return;
     }
 
-    var channels = vAPI.messaging.channels;
-    var channel, listener;
+    var messaging = vAPI.messaging;
+    var channels = messaging.channels;
+    var channel;
 
+    // Sent to all channels
     if ( response.broadcast === true && !response.channelName ) {
         for ( channel in channels ) {
-            if ( channels.hasOwnProperty(channel) === false ) {
+            if ( channels[channel] instanceof MessagingChannel === false ) {
                 continue;
             }
-            listener = channels[channel].listener;
-            if ( typeof listener === 'function' ) {
-                listener(response.msg);
-            }
+            channels[channel].listeners.process(response.msg);
         }
         return;
     }
 
+    // Response to specific message previously sent
     if ( response.requestId ) {
-        listener = vAPI.messaging.listeners[response.requestId];
-        delete vAPI.messaging.listeners[response.requestId];
-        delete response.requestId;
+        var listener = messaging.pending[response.requestId];
+        delete messaging.pending[response.requestId];
+        delete response.requestId; // TODO: why?
+        if ( listener ) {
+            listener(response.msg);
+            return;
+        }
     }
 
-    if ( !listener ) {
-        channel = channels[response.channelName];
-        listener = channel && channel.listener;
+    // Sent to a specific channel
+    channel = channels[response.channelName];
+    if ( channel instanceof MessagingChannel ) {
+        channel.listeners.process(response.msg);
     }
+};
 
-    if ( typeof listener === 'function' ) {
-        listener(response.msg);
+/******************************************************************************/
+
+var MessagingChannel = function(name, callback) {
+    this.channelName = name;
+    this.listeners = new MessagingListeners(callback);
+    this.refCount = 1;
+    if ( typeof callback === 'function' ) {
+        var messaging = vAPI.messaging;
+        if ( messaging.port === null ) {
+            messaging.setup();
+        }
     }
 };
 
+MessagingChannel.prototype.send = function(message, callback) {
+    var messaging = vAPI.messaging;
+    if ( messaging.port === null ) {
+        messaging.setup();
+    }
+    var requestId;
+    if ( callback ) {
+        requestId = messaging.requestId++;
+        messaging.pending[requestId] = callback;
+    }
+    messaging.port.postMessage({
+        channelName: this.channelName,
+        requestId: requestId,
+        msg: message
+    });
+};
+
+MessagingChannel.prototype.close = function() {
+    this.refCount -= 1;
+    if ( this.refCount !== 0 ) {
+        return;
+    }
+    var messaging = vAPI.messaging;
+    delete messaging.channels[this.channelName];
+    if ( Object.keys(messaging.channels).length === 0 ) {
+        messaging.close();
+    }
+};
+
+MessagingChannel.prototype.addListener = function(callback) {
+    if ( typeof callback !== 'function' ) {
+        return;
+    }
+    this.listeners.add(callback);
+    var messaging = vAPI.messaging;
+    if ( messaging.port === null ) {
+        messaging.setup();
+    }
+};
+
+MessagingChannel.prototype.removeListener = function(callback) {
+    if ( typeof callback !== 'function' ) {
+        return;
+    }
+    this.listeners.remove(callback);
+};
+
 /******************************************************************************/
 
 vAPI.messaging = {
     port: null,
     channels: {},
-    listeners: {},
+    pending: {},
     requestId: 1,
 
     setup: function() {
@@ -131,43 +230,21 @@ vAPI.messaging = {
         this.port.onMessage.removeListener(messagingConnector);
         this.port = null;
         this.channels = {};
-        this.listeners = {};
+        this.pending = {};
     },
 
     channel: function(channelName, callback) {
         if ( !channelName ) {
             return;
         }
-
-        this.channels[channelName] = {
-            channelName: channelName,
-            listener: typeof callback === 'function' ? callback : null,
-            send: function(message, callback) {
-                if ( vAPI.messaging.port === null ) {
-                    vAPI.messaging.setup();
-                }
-
-                message = {
-                    channelName: this.channelName,
-                    msg: message
-                };
-
-                if ( callback ) {
-                    message.requestId = vAPI.messaging.requestId++;
-                    vAPI.messaging.listeners[message.requestId] = callback;
-                }
-
-                vAPI.messaging.port.postMessage(message);
-            },
-            close: function() {
-                delete vAPI.messaging.channels[this.channelName];
-                if ( Object.keys(vAPI.messaging.channels).length === 0 ) {
-                    vAPI.messaging.close();
-                }
-            }
-        };
-
-        return this.channels[channelName];
+        var channel = this.channels[channelName];
+        if ( channel instanceof MessagingChannel ) {
+            channel.addListener(callback);
+            channel.refCount += 1;
+        } else {
+            channel = this.channels[channelName] = new MessagingChannel(channelName, callback);
+        }
+        return channel;
     }
 };
 
diff --git a/platform/chromium/vapi-common.js b/platform/chromium/vapi-common.js
index 0ddc7f486..4df7b9968 100644
--- a/platform/chromium/vapi-common.js
+++ b/platform/chromium/vapi-common.js
@@ -90,7 +90,11 @@ vAPI.closePopup = function() {
 // This storage is optional, but it is nice to have, for a more polished user
 // experience.
 
-vAPI.localStorage = window.localStorage;
+// This can throw in some contexts (like in devtool).
+try {
+    vAPI.localStorage = window.localStorage;
+} catch (ex) {
+}
 
 /******************************************************************************/
 
diff --git a/platform/firefox/bootstrap.js b/platform/firefox/bootstrap.js
index 440e9e198..fdca64775 100644
--- a/platform/firefox/bootstrap.js
+++ b/platform/firefox/bootstrap.js
@@ -26,6 +26,8 @@
 
 /******************************************************************************/
 
+const {classes: Cc} = Components;
+
 // Accessing the context of the background page:
 // var win = Services.appShell.hiddenDOMWindow.document.querySelector('iframe[src*=ublock0]').contentWindow;
 
@@ -34,7 +36,7 @@ let version;
 const hostName = 'ublock0';
 const restartListener = {
     get messageManager() {
-        return Components.classes['@mozilla.org/parentprocessmessagemanager;1']
+        return Cc['@mozilla.org/parentprocessmessagemanager;1']
             .getService(Components.interfaces.nsIMessageListenerManager);
     },
 
@@ -51,7 +53,7 @@ function startup(data, reason) {
         version = data.version;
     }
 
-    let appShell = Components.classes['@mozilla.org/appshell/appShellService;1']
+    let appShell = Cc['@mozilla.org/appshell/appShellService;1']
         .getService(Components.interfaces.nsIAppShellService);
 
     let onReady = function(e) {
@@ -96,7 +98,7 @@ function startup(data, reason) {
         return;
     }
 
-    let ww = Components.classes['@mozilla.org/embedcomp/window-watcher;1']
+    let ww = Cc['@mozilla.org/embedcomp/window-watcher;1']
         .getService(Components.interfaces.nsIWindowWatcher);
 
     ww.registerNotification({
@@ -141,7 +143,7 @@ function shutdown(data, reason) {
 
 function install(/*aData, aReason*/) {
     // https://bugzil.la/719376
-    Components.classes['@mozilla.org/intl/stringbundle;1']
+    Cc['@mozilla.org/intl/stringbundle;1']
         .getService(Components.interfaces.nsIStringBundleService)
         .flushBundles();
 }
diff --git a/platform/firefox/vapi-background.js b/platform/firefox/vapi-background.js
index 647c4c407..f7a4d7202 100644
--- a/platform/firefox/vapi-background.js
+++ b/platform/firefox/vapi-background.js
@@ -1026,7 +1026,6 @@ var tabWatcher = (function() {
             tabContainer.removeEventListener('TabSelect', onSelect);
         }
 
-        // Close extension tabs
         var browser, URI, tabId;
         for ( var tab of tabBrowser.tabs ) {
             browser = tabWatcher.browserFromTarget(tab);
@@ -1034,6 +1033,7 @@ var tabWatcher = (function() {
                 continue;
             }
             URI = browser.currentURI;
+            // Close extension tabs
             if ( URI.schemeIs('chrome') && URI.host === location.host ) {
                 vAPI.tabs._remove(tab, getTabBrowser(this));
             }
@@ -1239,6 +1239,35 @@ vAPI.messaging.setup = function(defaultHandler) {
 
 /******************************************************************************/
 
+vAPI.messaging.send = function(tabId, channelName, message) {
+    var ffTabId = tabId || '';
+    var targetId = location.host + ':broadcast';
+    var payload = JSON.stringify({ channelName: channelName, msg: message });
+
+    if ( ffTabId === '' ) {
+        this.globalMessageManager.broadcastAsyncMessage(targetId, payload);
+        return;
+    }
+
+    var browser = tabWatcher.browserFromTabId(ffTabId);
+    if ( browser === null ) {
+        return;
+    }
+
+    var messageManager = browser.messageManager || null;
+    if ( messageManager === null ) {
+        return;
+    }
+
+    if ( messageManager.sendAsyncMessage ) {
+        messageManager.sendAsyncMessage(targetId, payload);
+    } else {
+        messageManager.broadcastAsyncMessage(targetId, payload);
+    }
+};
+
+/******************************************************************************/
+
 vAPI.messaging.broadcast = function(message) {
     this.globalMessageManager.broadcastAsyncMessage(
         location.host + ':broadcast',
diff --git a/platform/firefox/vapi-client.js b/platform/firefox/vapi-client.js
index 88b11da09..44bbec0c3 100644
--- a/platform/firefox/vapi-client.js
+++ b/platform/firefox/vapi-client.js
@@ -67,66 +67,158 @@ vAPI.shutdown = (function() {
 
 /******************************************************************************/
 
+var MessagingListeners = function(callback) {
+    this.listeners = [];
+    if ( typeof callback === 'function' ) {
+        this.listeners.push(callback);
+    }
+};
+
+MessagingListeners.prototype.add = function(callback) {
+    if ( typeof callback !== 'function' ) {
+        return;
+    }
+    if ( this.listeners.indexOf(callback) !== -1 ) {
+        throw new Error('Duplicate listener.');
+    }
+    this.listeners.push(callback);
+};
+
+MessagingListeners.prototype.remove = function(callback) {
+    if ( typeof callback !== 'function' ) {
+        return;
+    }
+    if ( this.listeners.indexOf(callback) === -1 ) {
+        throw new Error('Listener not found.');
+    }
+    this.listeners.splice(this.listeners.indexOf(callback), 1);
+};
+
+MessagingListeners.prototype.process = function(msg) {
+    var listeners = this.listeners;
+    var n = listeners.length;
+    for ( var i = 0; i < n; i++ ) {
+        listeners[i](msg);
+    }
+};
+
+/******************************************************************************/
+
 var messagingConnector = function(response) {
     if ( !response ) {
         return;
     }
 
-    var channels = vAPI.messaging.channels;
-    var channel, listener;
+    var messaging = vAPI.messaging;
+    var channels = messaging.channels;
+    var channel;
 
+    // Sent to all channels
     if ( response.broadcast === true && !response.channelName ) {
         for ( channel in channels ) {
-            if ( channels.hasOwnProperty(channel) === false ) {
+            if ( channels[channel] instanceof MessagingChannel === false ) {
                 continue;
             }
-            listener = channels[channel].listener;
-            if ( typeof listener === 'function' ) {
-                listener(response.msg);
-            }
+            channels[channel].listeners.process(response.msg);
         }
         return;
     }
 
+    // Response to specific message previously sent
     if ( response.requestId ) {
-        listener = vAPI.messaging.listeners[response.requestId];
-        delete vAPI.messaging.listeners[response.requestId];
-        delete response.requestId;
+        var listener = messaging.pending[response.requestId];
+        delete messaging.pending[response.requestId];
+        delete response.requestId; // TODO: why?
+        if ( listener ) {
+            listener(response.msg);
+            return;
+        }
     }
 
-    if ( !listener ) {
-        channel = channels[response.channelName];
-        listener = channel && channel.listener;
+    // Sent to a specific channel
+    channel = channels[response.channelName];
+    if ( channel instanceof MessagingChannel ) {
+        channel.listeners.process(response.msg);
     }
+};
 
-    if ( typeof listener === 'function' ) {
-        listener(response.msg);
+/******************************************************************************/
+
+var MessagingChannel = function(name, callback) {
+    this.channelName = name;
+    this.listeners = new MessagingListeners(callback);
+    this.refCount = 1;
+    if ( typeof callback === 'function' ) {
+        var messaging = vAPI.messaging;
+        if ( !messaging.connected ) {
+            messaging.setup();
+        }
     }
 };
 
+MessagingChannel.prototype.send = function(message, callback) {
+    var messaging = vAPI.messaging;
+    if ( !messaging.connected ) {
+        messaging.setup();
+    }
+    var requestId;
+    if ( callback ) {
+        requestId = messaging.requestId++;
+        messaging.pending[requestId] = callback;
+    }
+    sendAsyncMessage('ublock0:background', {
+        channelName: self._sandboxId_ + '|' + this.channelName,
+        requestId: requestId,
+        msg: message
+    });
+};
+
+MessagingChannel.prototype.close = function() {
+    this.refCount -= 1;
+    if ( this.refCount !== 0 ) {
+        return;
+    }
+    delete vAPI.messaging.channels[this.channelName];
+};
+
+MessagingChannel.prototype.addListener = function(callback) {
+    if ( typeof callback !== 'function' ) {
+        return;
+    }
+    this.listeners.add(callback);
+    var messaging = vAPI.messaging;
+    if ( !messaging.connected ) {
+        messaging.setup();
+    }
+};
+
+MessagingChannel.prototype.removeListener = function(callback) {
+    if ( typeof callback !== 'function' ) {
+        return;
+    }
+    this.listeners.remove(callback);
+};
+
 /******************************************************************************/
 
 vAPI.messaging = {
     channels: {},
-    listeners: {},
+    pending: {},
     requestId: 1,
+    connected: false,
+    connector: function(msg) {
+        messagingConnector(JSON.parse(msg));
+    },
 
     setup: function() {
-        this.connector = function(msg) {
-            messagingConnector(JSON.parse(msg));
-        };
-
         addMessageListener(this.connector);
-
-        this.channels['vAPI'] = {};
-        this.channels['vAPI'].listener = function(msg) {
+        this.connected = true;
+        this.channels['vAPI'] = new MessagingChannel('vAPI', function(msg) {
             if ( msg.cmd === 'injectScript' ) {
                 var details = msg.details;
-
                 if ( !details.allFrames && window !== window.top ) {
                     return;
                 }
-
                 // TODO: investigate why this happens, and if this happens
                 // legitimately (content scripts not injected I suspect, so
                 // that would make this legitimate).
@@ -135,55 +227,35 @@ vAPI.messaging = {
                     self.injectScript(details.file);
                 }
             }
-        };
+        });
     },
 
     close: function() {
-        if ( !this.connector ) {
+        if ( !this.connected ) {
             return;
         }
-
         removeMessageListener();
-        this.connector = null;
+        this.connected = false;
         this.channels = {};
-        this.listeners = {};
+        this.pending = {};
     },
 
     channel: function(channelName, callback) {
         if ( !channelName ) {
             return;
         }
-
-        this.channels[channelName] = {
-            channelName: channelName,
-            listener: typeof callback === 'function' ? callback : null,
-            send: function(message, callback) {
-                if ( !vAPI.messaging.connector ) {
-                    vAPI.messaging.setup();
-                }
-
-                message = {
-                    channelName: self._sandboxId_ + '|' + this.channelName,
-                    msg: message
-                };
-
-                if ( callback ) {
-                    message.requestId = vAPI.messaging.requestId++;
-                    vAPI.messaging.listeners[message.requestId] = callback;
-                }
-
-                sendAsyncMessage('ublock0:background', message);
-            },
-            close: function() {
-                delete vAPI.messaging.channels[this.channelName];
-            }
-        };
-
-        return this.channels[channelName];
+        var channel = this.channels[channelName];
+        if ( channel instanceof MessagingChannel ) {
+            channel.addListener(callback);
+            channel.refCount += 1;
+        } else {
+            channel = this.channels[channelName] = new MessagingChannel(channelName, callback);
+        }
+        return channel;
     },
 
     toggleListener: function({type, persisted}) {
-        if ( !vAPI.messaging.connector ) {
+        if ( !vAPI.messaging.connected ) {
             return;
         }
 
diff --git a/src/css/logger-ui.css b/src/css/logger-ui.css
index 9c6379625..ee26f7ca7 100644
--- a/src/css/logger-ui.css
+++ b/src/css/logger-ui.css
@@ -4,24 +4,27 @@ body {
     box-sizing: border-box;
     color: black;
     -moz-box-sizing: border-box;
+    display: flex;
+    flex-direction: column;
+    height: 100vh;
+    justify-content: flex-start;
     margin: 0;
-    overflow-x: hidden;
+    overflow: hidden;
     padding: 0;
-    width: 100%;
+    width: 100vw;
     }
-#toolbar {
+input:focus {
+    background-color: #ffe;
+    }
+.permatoolbar {
     background-color: white;
     border: 0;
-    box-sizing: border-box;
-    left: 0;
+    font-size: 120%;
     margin: 0;
-    padding: 0.5em 1em;
-    position: fixed;
-    top: 0;
-    width: 100%;
+    padding: 0.25em 0.5em;
     z-index: 10;
     }
-#toolbar .button {
+.permatoolbar .button {
     background-color: white;
     border: none;
     box-sizing: border-box;
@@ -31,112 +34,195 @@ body {
     margin: 0;
     padding: 8px;
     }
-#toolbar .button.disabled {
+.permatoolbar .button.disabled {
     opacity: 0.2;
     pointer-events: none;
     }
-#toolbar .button:hover {
+.permatoolbar .button.active {
+    font-weight: bold;
+    }
+.permatoolbar .button:hover {
     background-color: #eee;
     }
-#toolbar > div {
+.permatoolbar > div {
     white-space: nowrap;
     }
-#toolbar > div:first-of-type {
-    font-size: 120%;
-    }
-#toolbar > div > * {
+.permatoolbar > div > * {
     vertical-align: middle;
     }
 #pageSelector {
     width: 28em;
     padding: 0.2em 0;
     }
-body #compactViewToggler.button:before {
-    content: '\f102';
+
+#domInspector {
+    border-top: 1px solid #ccc;
+    display: none;
+    max-height: 40%;
+    min-height: 40%;
+    overflow: auto;
     }
-body.compactView #compactViewToggler.button:before {
-    content: '\f103';
+#domInspector.enabled {
+    display: block;
     }
-#filterButton {
-    opacity: 0.25;
+#domInspector > ul:first-child {
+    padding-left: 0;
     }
-body.f #filterButton {
-    opacity: 1;
+#domInspector ul {
+    background-color: #fff;
+    margin: 0;
+    padding-left: 1em;
     }
-#filterInput.bad {
+#domInspector li {
+    list-style-type: none;
+    white-space: nowrap;
+    }
+#domInspector li.isCosmeticHide,
+#domInspector li.isCosmeticHide ul,
+#domInspector li.isCosmeticHide li {
     background-color: #fee;
     }
-#maxEntries {
-    margin: 0 2em;
+#domInspector li > * {
+    margin-right: 1em;
     }
-input:focus {
-    background-color: #ffe;
+#domInspector li > span:first-child {
+    color: #000;
+    cursor: default;
+    display: inline-block;
+    margin-right: 0;
+    opacity: 0.5;
+    visibility: hidden;
+    width: 1em;
     }
-#content {
-    font: 13px sans-serif;
-    width: 100%;
+#domInspector li > span:first-child:hover {
+    opacity: 1;
+    }
+#domInspector li > *:last-child {
+    margin-right: 0;
+    }
+#domInspector li > span:first-child:before {
+    content: '\a0';
+    }
+#domInspector li.branch > span:first-child:before {
+    content: '\25b8';
+    visibility: visible;
+    }
+#domInspector li.branch.show > span:first-child:before {
+    content: '\25be';
+    visibility: visible;
+    }
+#domInspector li.branch.hasCosmeticHide > span:first-child:before {
+    color: red;
+    }
+#domInspector li > code {
+    cursor: pointer;
+    font: 12px/1.4 monospace;
+    }
+#domInspector li > code.off {
+    text-decoration: line-through;
+    }
+#domInspector li > span {
+    color: #aaa;
+    }
+#domInspector li > code.filter {
+    color: red;
+    }
+#domInspector li > ul {
+    display: none;
+    }
+#domInspector li.show > ul {
+    display: block;
     }
 
-#content table {
+#events {
+    border-top: 1px solid #ccc;
+    font: 13px sans-serif;
+    min-height: 60%;
+    overflow-x: hidden;
+    overflow-y: auto;
+    width: 100%;
+    }
+#events .permatoolbar {
+    position: absolute;
+    }
+#events #compactViewToggler.button:before {
+    content: '\f102';
+    }
+#events.compactView #compactViewToggler.button:before {
+    content: '\f103';
+    }
+#events #filterButton {
+    opacity: 0.25;
+    }
+#events.f #filterButton {
+    opacity: 1;
+    }
+#events #filterInput.bad {
+    background-color: #fee;
+    }
+#events #maxEntries {
+    margin: 0 2em;
+    }
+#events table {
     border: 0;
     border-collapse: collapse;
     direction: ltr;
     table-layout: fixed;
     width: 100%;
     }
-#content table > colgroup > col:nth-of-type(1) {
+#events table > colgroup > col:nth-of-type(1) {
     width: 5em;
     }
-#content table > colgroup > col:nth-of-type(2) {
+#events table > colgroup > col:nth-of-type(2) {
     width: 2.5em;
     }
-#content table > colgroup > col:nth-of-type(3) {
+#events table > colgroup > col:nth-of-type(3) {
     width: 20%;
     }
-#content table > colgroup > col:nth-of-type(4) {
+#events table > colgroup > col:nth-of-type(4) {
     width: 2.5em;
     }
-#content table > colgroup > col:nth-of-type(5) {
+#events table > colgroup > col:nth-of-type(5) {
     width: 6em;
     }
-#content table > colgroup > col:nth-of-type(6) {
+#events table > colgroup > col:nth-of-type(6) {
     width: calc(100% - 16em - 20%);
     }
-body.f #content table tr.f {
+#events.f table tr.f {
     display: none;
     }
 
-#content tr.cat_info {
+#events tr.cat_info {
     color: #00f;
     }
-#content tr.blocked {
+#events tr.blocked {
     background-color: rgba(192, 0, 0, 0.1);
     }
-body.colorBlind #content tr.blocked {
+body.colorBlind #events tr.blocked {
     background-color: rgba(0, 19, 110, 0.1);
     }
-#content tr.nooped {
+#events tr.nooped {
     background-color: rgba(108, 108, 108, 0.1);
     }
-body.colorBlind #content tr.nooped {
+body.colorBlind #events tr.nooped {
     background-color: rgba(96, 96, 96, 0.1);
     }
-#content tr.allowed {
+#events tr.allowed {
     background-color: rgba(0, 160, 0, 0.1);
     }
-body.colorBlind #content tr.allowed {
+body.colorBlind #events tr.allowed {
     background-color: rgba(255, 194, 57, 0.1)
     }
-#content tr.cb {
+#events tr.cb {
     background-color: rgba(255, 255, 0, 0.1);
     }
-#content tr.maindoc {
+#events tr.maindoc {
     background-color: #666;
     color: white;
     text-align: center;
     }
 
-body #content td {
+body #events td {
     border: 1px solid #ccc;
     border-top: none;
     min-width: 0.5em;
@@ -146,87 +232,87 @@ body #content td {
     word-break: break-all;
     word-wrap: break-word;
     }
-#content tr td {
+#events tr td {
     border-top: 1px solid #ccc;
     }
-#content tr td:first-of-type {
+#events tr td:first-of-type {
     border-left: none;
     }
-#content tr td:last-of-type {
+#events tr td:last-of-type {
     border-right: none;
     }
-body.compactView #content td {
+#events.compactView td {
     overflow: hidden;
     text-overflow: ellipsis;
     white-space: nowrap;
     }
 
-#content tr td:nth-of-type(1) {
+#events tr td:nth-of-type(1) {
     text-align: right;
     white-space: nowrap;
     }
-#content tr td:nth-of-type(2) {
+#events tr td:nth-of-type(2) {
     text-align: center;
     white-space: nowrap;
     }
-#content tr.tab_bts > td:nth-of-type(2):before {
+#events tr.tab_bts > td:nth-of-type(2):before {
     content: '\f070';
     font: 1em FontAwesome;
     }
-#content tr.tab:not(.canMtx) {
+#events tr.tab:not(.canMtx) {
     opacity: 0.3;
     }
-#content tr.tab:not(.canMtx):hover {
+#events tr.tab:not(.canMtx):hover {
     opacity: 0.7;
     }
-#content tr.tab:not(.canMtx) > td:nth-of-type(2):before {
+#events tr.tab:not(.canMtx) > td:nth-of-type(2):before {
     content: '\f00d';
     font: 1em FontAwesome;
     }
-body:not(.popupOn) #content tr.canMtx td:nth-of-type(2) {
+body:not(.popupOn) #events tr.canMtx td:nth-of-type(2) {
     cursor: zoom-in;
     }
-body:not(.popupOn) #content tr.canMtx td:nth-of-type(2):hover {
+body:not(.popupOn) #events tr.canMtx td:nth-of-type(2):hover {
     background: #ccc;
     }
-#content tr.canLookup td:nth-of-type(3) {
+#events tr.canLookup td:nth-of-type(3) {
     cursor: zoom-in;
     }
-#content tr.cat_net td:nth-of-type(4),
-#content tr.cat_cosmetic td:nth-of-type(4) {
+#events tr.cat_net td:nth-of-type(4),
+#events tr.cat_cosmetic td:nth-of-type(4) {
     font: 12px monospace;
     text-align: center;
     white-space: nowrap;
     }
-#content tr.cat_net td:nth-of-type(4) {
+#events tr.cat_net td:nth-of-type(4) {
     cursor: pointer;
     position: relative;
     }
-#content tr.cat_net td:nth-of-type(4):hover {
+#events tr.cat_net td:nth-of-type(4):hover {
     background: #ccc;
     }
-#content tr.cat_net td:nth-of-type(6) > span > b {
+#events tr.cat_net td:nth-of-type(6) > span > b {
     font-weight: bold;
     }
-#content tr td:nth-of-type(6) b {
+#events tr td:nth-of-type(6) b {
     font-weight: normal;
     }
-#content tr.blocked td:nth-of-type(6) b {
+#events tr.blocked td:nth-of-type(6) b {
     background-color: rgba(192, 0, 0, 0.2);
     }
-body.colorBlind #content tr.blocked td:nth-of-type(6) b {
+body.colorBlind #events tr.blocked td:nth-of-type(6) b {
     background-color: rgba(0, 19, 110, 0.2);
     }
-#content tr.nooped td:nth-of-type(6) b {
+#events tr.nooped td:nth-of-type(6) b {
     background-color: rgba(108, 108, 108, 0.2);
     }
-body.colorBlind #content tr.nooped td:nth-of-type(6) b {
+body.colorBlind #events tr.nooped td:nth-of-type(6) b {
     background-color: rgba(96, 96, 96, 0.2);
     }
-#content tr.allowed td:nth-of-type(6) b {
+#events tr.allowed td:nth-of-type(6) b {
     background-color: rgba(0, 160, 0, 0.2);
     }
-body.colorBlind #content tr.allowed td:nth-of-type(6) b {
+body.colorBlind #events tr.allowed td:nth-of-type(6) b {
     background-color: rgba(255, 194, 57, 0.2);
     }
 
@@ -242,7 +328,7 @@ body.colorBlind #content tr.allowed td:nth-of-type(6) b {
     top: 0;
     z-index: 200;
     }
-body.popupOn #popupContainer {
+#events.popupOn #popupContainer {
     display: block;
     }
 #popupContainer > div {
diff --git a/src/epicker.html b/src/epicker.html
index f3456b086..4e011e2f8 100644
--- a/src/epicker.html
+++ b/src/epicker.html
@@ -6,11 +6,11 @@
 }
 html, body {
     background: transparent !important;
-    margin: 0;
-    width: 100%;
-    height: 100%;
-    overflow: hidden;
     font: 12px sans-serif;
+    height: 100%;
+    margin: 0;
+    overflow: hidden;
+    width: 100%;
 }
 ul, li, div {
     display: block;
@@ -43,9 +43,6 @@ button:not(:disabled):hover {
 #create:not(:disabled) {
     background-color: #ffdca8;
 }
-aside {
-    background-color: #eee;
-}
 section {
     border: 0;
     box-sizing: border-box;
@@ -80,7 +77,7 @@ ul {
     overflow: hidden;
 }
 aside > ul {
-    height: 12em;
+    height: 16em;
     overflow-y: auto;
 }
 aside > ul > li:first-of-type {
@@ -129,16 +126,20 @@ svg > path + path {
     fill: rgba(255,31,31,0.25);
 }
 aside {
+    background-color: #eee;
     bottom: 4px;
+    box-sizing: border-box;
+    visibility: hidden;
+    height: calc(40% - 4px);
     padding: 4px;
-    display: none;
     position: fixed;
     right: 4px;
-    width: 30em;
+    width: calc(40% - 4px);
 }
 body.paused > aside {
-    opacity: 0.2;
-    display: block;
+    opacity: 0.1;
+    visibility: visible;
+    z-index: 100;
 }
 body.paused > aside:hover {
     opacity: 1;
diff --git a/src/js/logger-ui.js b/src/js/logger-ui.js
index 192f14eb9..576360a09 100644
--- a/src/js/logger-ui.js
+++ b/src/js/logger-ui.js
@@ -32,15 +32,24 @@
 
 // Adjust top padding of content table, to match that of toolbar height.
 
-uDom.nodeFromId('content').style.setProperty(
-    'margin-top',
-    uDom.nodeFromId('toolbar').offsetHeight + 'px'
-);
+(function() {
+    var parent = uDom.nodeFromSelector('body > .permatoolbar');
+    var child = parent.firstElementChild;
+    var size = child.clientHeight + 'px';
+    parent.style.setProperty('min-height', size);
+
+    parent = uDom.nodeFromId('events');
+    parent.querySelector('table').style.setProperty(
+        'margin-top',
+        parent.querySelector('.permatoolbar').clientHeight + 'px'
+    );
+})();
 
 /******************************************************************************/
 
 var messager = vAPI.messaging.channel('logger-ui.js');
-var tbody = document.querySelector('#content tbody');
+
+var tbody = document.querySelector('#events tbody');
 var trJunkyard = [];
 var tdJunkyard = [];
 var firstVarDataCol = 2;  // currently, column 2 (0-based index)
@@ -89,6 +98,14 @@ var dateOptions = {
 
 /******************************************************************************/
 
+var removeAllChildren = function(node) {
+    while ( node.firstChild ) {
+        node.removeChild(node.firstChild);
+    }
+};
+
+/******************************************************************************/
+
 var classNameFromTabId = function(tabId) {
     if ( tabId === noTabId ) {
         return 'tab_bts';
@@ -109,6 +126,427 @@ var tabIdFromClassName = function(className) {
     return matches[1];
 };
 
+/******************************************************************************/
+/******************************************************************************/
+
+// DOM inspector
+
+(function domInspector() {
+    // Don't bother if the browser is not modern enough.
+    if ( typeof Map === undefined ) {
+        return;
+    }
+
+    var enabled = false;
+    var state = '';
+    var fingerprint = '';
+    var fingerprintTimer = null;
+    var currentTabId = '';
+    var currentSelector = '';
+    var inspector = uDom.nodeFromId('domInspector');
+    var tabSelector = uDom.nodeFromId('pageSelector');
+
+    var inlineElementTags = [
+        'a', 'abbr', 'acronym',
+        'b', 'bdo', 'big', 'br', 'button',
+        'cite', 'code',
+        'del', 'dfn',
+        'em',
+        'font',
+        'i', 'img', 'input', 'ins',
+        'kbd',
+        'label',
+        'map',
+        'object',
+        'q',
+        'samp', 'select', 'small', 'span', 'strong', 'sub', 'sup',
+        'textarea', 'tt',
+        'u',
+        'var'
+    ].reduce(function(p, c) {
+        p[c] = true;
+        return p;
+    }, Object.create(null));
+
+    var startTimer = function() {
+        if ( fingerprintTimer === null ) {
+            fingerprintTimer = vAPI.setTimeout(fetchFingerprint, 2000);
+        }
+    };
+
+    var stopTimer = function() {
+        if ( fingerprintTimer !== null ) {
+            clearTimeout(fingerprintTimer);
+            fingerprintTimer = null;
+        }
+    };
+
+    var injectHighlighter = function(tabId) {
+        if ( tabId === '' ) {
+            return;
+        }
+        messager.send({
+            what: 'scriptlet',
+            tabId: tabId,
+            scriptlet: 'dom-highlight'
+        });
+    };
+
+    var removeHighlighter = function(tabId) {
+        if ( tabId === '' ) {
+            return;
+        }
+        messager.send({
+            what: 'sendMessageTo',
+            tabId: tabId,
+            channelName: 'scriptlets',
+            msg: {
+                what: 'dom-highlight',
+                action: 'shutdown'
+            }
+        });
+    };
+
+    var nodeFromDomEntry = function(entry) {
+        var node;
+        var li = document.createElement('li');
+        // expander/collapser
+        node = document.createElement('span');
+        li.appendChild(node);
+        // selector
+        node = document.createElement('code');
+        node.textContent = entry.sel;
+        li.appendChild(node);
+        // descendant count
+        if ( entry.cnt !== 0 ) {
+            node = document.createElement('span');
+            node.textContent = entry.cnt.toLocaleString();
+            li.appendChild(node);
+        }
+        // cosmetic filter
+        if ( entry.filter !== undefined ) {
+            node = document.createElement('code');
+            node.classList.add('filter');
+            node.textContent = entry.filter;
+            li.appendChild(node);
+            li.classList.add('isCosmeticHide');
+        }
+        return li;
+    };
+
+    var appendListItem = function(ul, li) {
+        ul.appendChild(li);
+        // Ancestor nodes of a node which is affected by a cosmetic filter will
+        // be marked as "containing cosmetic filters", for user convenience.
+        if ( li.classList.contains('isCosmeticHide') === false ) {
+            return;
+        }
+        for (;;) {
+            li = li.parentElement.parentElement;
+            if ( li === null ) {
+                break;
+            }
+            li.classList.add('hasCosmeticHide');
+        }
+    };
+
+    var expandIfBlockElement = function(node) {
+        var ul = node.parentElement;
+        if ( ul === null ) {
+            return;
+        }
+        var li = ul.parentElement;
+        if ( li === null ) {
+            return;
+        }
+        if ( li.classList.contains('show') ) {
+            return;
+        }
+        var tag = node.firstElementChild.textContent;
+        var pos = tag.search(/[^a-z0-9]/);
+        if ( pos !== -1 ) {
+            tag = tag.slice(0, pos);
+        }
+        if ( inlineElementTags[tag] !== undefined ) {
+            return;
+        }
+        li.classList.add('show');
+    };
+
+    var renderDOM = function(response) {
+        var ul = document.createElement('ul');
+        var lvl = 0;
+        var entries = response;
+        var n = entries.length;
+        var li, entry;
+        for ( var i = 0; i < n; i++ ) {
+            entry = entries[i];
+            if ( entry.lvl === lvl ) {
+                li = nodeFromDomEntry(entry);
+                appendListItem(ul, li);
+                //expandIfBlockElement(li);
+                continue;
+            }
+            if ( entry.lvl > lvl ) {
+                ul = document.createElement('ul');
+                li.appendChild(ul);
+                li.classList.add('branch');
+                li = nodeFromDomEntry(entry);
+                appendListItem(ul, li);
+                //expandIfBlockElement(li);
+                lvl = entry.lvl;
+                continue;
+            }
+            // entry.lvl < lvl
+            while ( entry.lvl < lvl ) {
+                ul = li.parentNode;
+                li = ul.parentNode;
+                ul = li.parentNode;
+                lvl -= 1;
+            }
+            li = nodeFromDomEntry(entry);
+            ul.appendChild(li);
+        }
+        while ( ul.parentNode !== null ) {
+            ul = ul.parentNode;
+        }
+        ul.firstElementChild.classList.add('show');
+
+        removeAllChildren(inspector);
+        inspector.appendChild(ul);
+
+        // Check for change at regular interval.
+        fingerprint = entries.length !== 0 ? entries[0].fp : '';
+    };
+
+    var selectorFromNode = function(node, nth) {
+        var selector = '';
+        var code;
+        if ( nth === undefined ) {
+            nth = 1;
+        }
+        while ( node !== null ) {
+            if ( node.localName === 'li' ) {
+                code = node.querySelector('code:nth-of-type(' + nth + ')');
+                if ( code !== null ) {
+                    selector = code.textContent + ' > ' + selector;
+                    if ( selector.indexOf('#') !== -1 ) {
+                        break;
+                    }
+                    nth = 1;
+                }
+            }
+            node = node.parentElement;
+        }
+        return selector.slice(0, -3);
+    };
+
+    var onClick = function(ev) {
+        ev.stopPropagation();
+
+        if ( currentTabId === '' ) {
+            return;
+        }
+
+        var target = ev.target;
+        var parent = target.parentElement;
+
+        // Expand/collapse branch
+        if (
+            target.localName === 'span' &&
+            parent instanceof HTMLLIElement &&
+            parent.classList.contains('branch') &&
+            target === parent.firstElementChild
+        ) {
+            target.parentElement.classList.toggle('show');
+            return;
+        }
+
+        // Toggle selector
+        if ( target.localName === 'code' ) {
+            var original = target.classList.contains('filter') === false;
+            messager.send({
+                what: 'sendMessageTo',
+                tabId: currentTabId,
+                channelName: 'scriptlets',
+                msg: {
+                    what: 'dom-highlight',
+                    action: 'toggleNodes',
+                    original: original,
+                    target: original !== target.classList.toggle('off'),
+                    selector: selectorFromNode(target, original ? 1 : 2)
+                }
+            });
+            return;
+        }
+
+        // Highlight and scrollto
+        if ( target.localName === 'code' ) {
+            messager.send({
+                what: 'sendMessageTo',
+                tabId: currentTabId,
+                channelName: 'scriptlets',
+                msg: {
+                    what: 'dom-highlight',
+                    action: 'highlight',
+                    selector: selectorFromNode(target),
+                    scrollTo: true
+                }
+            });
+            return;
+        }
+    };
+
+    var onMouseOver = (function() {
+        var mouseoverTarget = null;
+        var mouseoverTimer = null;
+
+        var timerHandler = function() {
+            mouseoverTimer = null;
+            messager.send({
+                what: 'sendMessageTo',
+                tabId: currentTabId,
+                channelName: 'scriptlets',
+                msg: {
+                    what: 'dom-highlight',
+                    action: 'highlight',
+                    selector: selectorFromNode(mouseoverTarget),
+                    scrollTo: true
+                }
+            });
+        };
+
+        return function(ev) {
+            // Find closest `li`
+            var target = ev.target;
+            while ( target !== null ) {
+                if ( target.localName === 'li' ) {
+                    break;
+                }
+                target = target.parentElement;
+            }
+            if ( target === mouseoverTarget ) {
+                return;
+            }
+            mouseoverTarget = target;
+            if ( mouseoverTimer === null ) {
+                mouseoverTimer = vAPI.setTimeout(timerHandler, 50);
+            }
+        };
+    })();
+
+    var onFingerprintFetched = function(response) {
+        if ( state !== 'fetchingFingerprint' ) {
+            return;
+        }
+        state = '';
+        fingerprintTimer = null;
+        if ( !enabled ) {
+            return;
+        }
+        if ( response === fingerprint ) {
+            startTimer();
+            return;
+        }
+        fingerprint = response || '';
+        fetchDOM();
+    };
+
+    var fetchFingerprint = function() {
+        messager.send({
+            what: 'scriptlet',
+            tabId: currentTabId,
+            scriptlet: 'dom-fingerprint'
+        }, onFingerprintFetched);
+        state = 'fetchingFingerprint';
+    };
+
+    var onDOMFetched = function(response) {
+        if ( state !== 'fetchingDOM' ) {
+            return;
+        }
+        state = '';
+        if ( !enabled ) {
+            return;
+        }
+        if ( Array.isArray(response) && response.length !== 0 ) {
+            renderDOM(response);
+            injectHighlighter(currentTabId);
+        } else {
+            fingerprint = '';
+        }
+        startTimer();
+    };
+
+    var fetchDOM = function() {
+        if ( currentTabId === '' ) {
+            removeAllChildren(inspector);
+            startTimer();
+            return;
+        }
+
+        messager.send({
+            what: 'scriptlet',
+            tabId: currentTabId,
+            scriptlet: 'dom-layout'
+        }, onDOMFetched);
+        state = 'fetchingDOM';
+    };
+
+    var onTabIdChanged = function() {
+        if ( !enabled ) {
+            return;
+        }
+        var previousTabId = currentTabId;
+        var tabId = tabIdFromClassName(tabSelector.value) || '';
+        currentTabId = tabId !== 'bts' && tabId !== '' ? tabId : '';
+        if ( currentTabId !== previousTabId ) {
+            removeHighlighter(previousTabId);
+        }
+        if ( state === 'fetchingDOM' ) {
+            return;
+        }
+        fetchDOM();
+    };
+
+    var toggleOn = function() {
+        if ( enabled ) {
+            return;
+        }
+        enabled = true;
+        window.addEventListener('beforeunload', toggleOff);
+        inspector.addEventListener('click', onClick, true);
+        inspector.addEventListener('mouseover', onMouseOver, true);
+        tabSelector.addEventListener('change', onTabIdChanged);
+        onTabIdChanged();
+        inspector.classList.add('enabled');
+    };
+
+    var toggleOff = function() {
+        removeHighlighter(currentTabId);
+        window.removeEventListener('beforeunload', toggleOff);
+        inspector.removeEventListener('click', onClick, true);
+        inspector.removeEventListener('mouseover', onMouseOver, true);
+        tabSelector.removeEventListener('change', onTabIdChanged);
+        removeAllChildren(inspector);
+        stopTimer();
+        currentTabId = currentSelector = fingerprint = '';
+        enabled = false;
+        inspector.classList.remove('enabled');
+    };
+
+    var toggle = function() {
+        if ( uDom.nodeFromId('showdom').classList.toggle('active') ) {
+            toggleOn();
+        } else {
+            toggleOff();
+        }
+    };
+
+    uDom('#showdom').on('click', toggle);
+})();
+
+/******************************************************************************/
 /******************************************************************************/
 
 var regexFromURLFilteringResult = function(result) {
@@ -238,14 +676,17 @@ var filterDecompiler = (function() {
         }
 
         // Filter options
+        // Importance
         if ( bits & 0x02 ) {
             opts.push('important');
         }
+        // Party
         if ( bits & 0x08 ) {
             opts.push('third-party');
         } else if ( bits & 0x04 ) {
             opts.push('first-party');
         }
+        // Type
         var typeVal = bits >>> 4 & 0x0F;
         if ( typeVal ) {
             opts.push(typeValToTypeName[typeVal]);
@@ -552,25 +993,14 @@ var renderLogEntries = function(response) {
     // dynamically refreshed pages.
     truncateLog(maxEntries);
 
+    // Follow waterfall if not observing top of waterfall.
     var yDelta = tbody.offsetHeight - height;
     if ( yDelta === 0 ) {
         return;
     }
-
-    // Chromium:
-    //   body.scrollTop = good value
-    //   body.parentNode.scrollTop = 0
-    if ( document.body.scrollTop !== 0 ) {
-        document.body.scrollTop += yDelta;
-        return;
-    }
-
-    // Firefox:
-    //   body.scrollTop = 0
-    //   body.parentNode.scrollTop = good value
-    var parentNode = document.body.parentNode;
-    if ( parentNode && parentNode.scrollTop !== 0 ) {
-        parentNode.scrollTop += yDelta;
+    var container = uDom.nodeFromId('events');
+    if ( container.scrollTop !== 0 ) {
+        container.scrollTop += yDelta;
     }
 };
 
@@ -648,7 +1078,7 @@ var truncateLog = function(size) {
     if ( size === 0 ) {
         size = 5000;
     }
-    var tbody = document.querySelector('#content tbody');
+    var tbody = document.querySelector('#events tbody');
     size = Math.min(size, 10000);
     var tr;
     while ( tbody.childElementCount > size ) {
@@ -715,11 +1145,11 @@ var pageSelectorChanged = function() {
     }
     if ( tabClass !== '' ) {
         sheet.insertRule(
-            '#content table tr:not(.' + tabClass + ') { display: none; }',
+            '#events table tr:not(.' + tabClass + ') { display: none; }',
             0
         );
     }
-    uDom('#refresh').toggleClass(
+    uDom('.needtab').toggleClass(
         'disabled',
         tabClass === '' || tabClass === 'tab_bts'
     );
@@ -780,12 +1210,6 @@ var netFilteringManager = (function() {
     var targetPageDomain;
     var targetFrameDomain;
 
-    var removeAllChildren = function(node) {
-        while ( node.firstChild ) {
-            node.removeChild(node.firstChild);
-        }
-    };
-
     var uglyTypeFromSelector = function(pane) {
         var prettyType = selectValue('select.type.' + pane);
         if ( pane === 'static' ) {
@@ -1495,10 +1919,10 @@ var rowFilterer = (function() {
     var filterAll = function() {
         // Special case: no filter
         if ( filters.length === 0 ) {
-            uDom('#content tr').removeClass('f');
+            uDom('#events tr').removeClass('f');
             return;
         }
-        var tbody = document.querySelector('#content tbody');
+        var tbody = document.querySelector('#events tbody');
         var rows = tbody.rows;
         var i = rows.length;
         while ( i-- ) {
@@ -1522,8 +1946,7 @@ var rowFilterer = (function() {
     })();
 
     var onFilterButton = function() {
-        var cl = document.body.classList;
-        cl.toggle('f', cl.contains('f') === false);
+        uDom.nodeFromId('events').classList.toggle('f');
     };
 
     uDom('#filterButton').on('click', onFilterButton);
@@ -1554,7 +1977,7 @@ var toJunkyard = function(trs) {
 
 var clearBuffer = function() {
     var tabId = uDom.nodeFromId('pageSelector').value || null;
-    var tbody = document.querySelector('#content tbody');
+    var tbody = document.querySelector('#events tbody');
     var tr = tbody.lastElementChild;
     var trPrevious;
     while ( tr !== null ) {
@@ -1577,7 +2000,7 @@ var clearBuffer = function() {
 /******************************************************************************/
 
 var cleanBuffer = function() {
-    var rows = uDom('#content tr.tab:not(.canMtx)').remove();
+    var rows = uDom('#events tr.tab:not(.canMtx)').remove();
     var i = rows.length;
     while ( i-- ) {
         trJunkyard.push(rows.nodeAt(i));
@@ -1588,10 +2011,7 @@ var cleanBuffer = function() {
 /******************************************************************************/
 
 var toggleCompactView = function() {
-    document.body.classList.toggle(
-        'compactView',
-        document.body.classList.contains('compactView') === false
-    );
+    uDom.nodeFromId('events').classList.toggle('compactView');
 };
 
 /******************************************************************************/
@@ -1604,7 +2024,7 @@ var popupManager = (function() {
     var popupObserver = null;
     var style = null;
     var styleTemplate = [
-        '#content tr:not(.tab_{{tabId}}) {',
+        '#events tr:not(.tab_{{tabId}}) {',
             'cursor: not-allowed;',
             'opacity: 0.2;',
         '}'
@@ -1659,11 +2079,15 @@ var popupManager = (function() {
         style = uDom.nodeFromId('popupFilterer');
         style.textContent = styleTemplate.replace('{{tabId}}', localTabId);
 
-        document.body.classList.add('popupOn');
+        var parent = uDom.nodeFromId('events');
+        var rect = parent.getBoundingClientRect();
+        container.style.setProperty('top', rect.top + 'px');
+        container.style.setProperty('right', (rect.right - parent.clientWidth) + 'px');
+        parent.classList.add('popupOn');
     };
 
     var toggleOff = function() {
-        document.body.classList.remove('popupOn');
+        uDom.nodeFromId('events').classList.remove('popupOn');
 
         container.querySelector('div > span:nth-of-type(1)').removeEventListener('click', toggleSize);
         container.querySelector('div > span:nth-of-type(2)').removeEventListener('click', toggleOff);
@@ -1714,9 +2138,9 @@ uDom.onLoad(function() {
     uDom('#clean').on('click', cleanBuffer);
     uDom('#clear').on('click', clearBuffer);
     uDom('#maxEntries').on('change', onMaxEntriesChanged);
-    uDom('#content table').on('click', 'tr.canMtx > td:nth-of-type(2)', popupManager.toggleOn);
-    uDom('#content').on('click', 'tr.cat_net > td:nth-of-type(4)', netFilteringManager.toggleOn);
-    uDom('#content').on('click', 'tr.canLookup > td:nth-of-type(3)', reverseLookupManager.toggleOn);
+    uDom('#events table').on('click', 'tr.canMtx > td:nth-of-type(2)', popupManager.toggleOn);
+    uDom('#events').on('click', 'tr.canLookup > td:nth-of-type(3)', reverseLookupManager.toggleOn);
+    uDom('#events').on('click', 'tr.cat_net > td:nth-of-type(4)', netFilteringManager.toggleOn);
 
     // https://github.com/gorhill/uBlock/issues/404
     // Ensure page state is in sync with the state of its various widgets.
diff --git a/src/js/messaging.js b/src/js/messaging.js
index 215fbd389..41e563bca 100644
--- a/src/js/messaging.js
+++ b/src/js/messaging.js
@@ -62,10 +62,6 @@ var onMessage = function(request, sender, callback) {
         µb.assets.get(request.url, callback);
         return;
 
-    case 'reloadAllFilters':
-        µb.reloadAllFilters(callback);
-        return;
-
     case 'listsFromNetFilter':
         µb.staticFilteringReverseLookup.fromNetFilter(
             request.compiledFilter,
@@ -82,6 +78,14 @@ var onMessage = function(request, sender, callback) {
         );
         return;
 
+    case 'reloadAllFilters':
+        µb.reloadAllFilters(callback);
+        return;
+
+    case 'scriptlet':
+        µb.scriptlets.inject(request.tabId, request.scriptlet, callback);
+        return;
+
     default:
         break;
     }
@@ -137,10 +141,6 @@ var onMessage = function(request, sender, callback) {
         vAPI.tabs.open(request.details);
         break;
 
-    case 'scriptletGotoImageURL':
-        µb.scriptletGotoImageURL(request);
-        break;
-
     case 'reloadTab':
         if ( vAPI.isBehindTheSceneTabId(request.tabId) === false ) {
             vAPI.tabs.reload(request.tabId);
@@ -150,10 +150,18 @@ var onMessage = function(request, sender, callback) {
         }
         break;
 
+    case 'scriptletResponse':
+        µb.scriptlets.report(tabId, request.scriptlet, request.response);
+        break;
+
     case 'selectFilterLists':
         µb.selectFilterLists(request.switches);
         break;
 
+    case 'sendMessageTo':
+        vAPI.messaging.send(request.tabId, request.channelName, request.msg);
+        break;
+
     case 'toggleHostnameSwitch':
         µb.toggleHostnameSwitch(request);
         break;
@@ -350,7 +358,7 @@ var getPopupDataLazy = function(tabId, callback) {
         return;
     }
 
-    µb.surveyCosmeticFilters(tabId, function() {
+    µb.scriptlets.inject(tabId, 'cosmetic-survey', function() {
         r.hiddenElementCount = pageStore.hiddenElementCount;
         callback(r);
     });
@@ -1373,6 +1381,8 @@ var logCosmeticFilters = function(tabId, details) {
 /******************************************************************************/
 
 var onMessage = function(request, sender, callback) {
+    var tabId = sender && sender.tab ? sender.tab.id : 0;
+
     // Async
     switch ( request.what ) {
     default:
@@ -1381,13 +1391,8 @@ var onMessage = function(request, sender, callback) {
 
     // Sync
     var response;
-    var tabId = sender && sender.tab ? sender.tab.id : 0;
 
     switch ( request.what ) {
-    case 'gotoImageURL':
-        response = µb.scriptlets.gotoImageURL;
-        break;
-
     case 'liveCosmeticFilteringData':
         var pageStore = µb.pageStoreFromTabId(tabId);
         if ( pageStore ) {
@@ -1412,4 +1417,40 @@ vAPI.messaging.listen('scriptlets', onMessage);
 
 })();
 
+
+/******************************************************************************/
+/******************************************************************************/
+
+// devtools
+
+(function() {
+
+'use strict';
+
+/******************************************************************************/
+
+var onMessage = function(request, sender, callback) {
+    // Async
+    switch ( request.what ) {
+    default:
+        break;
+    }
+
+    // Sync
+    var response;
+
+    switch ( request.what ) {
+    default:
+        return vAPI.messaging.UNHANDLED;
+    }
+
+    callback(response);
+};
+
+vAPI.messaging.listen('devtools', onMessage);
+
+/******************************************************************************/
+
+})();
+
 /******************************************************************************/
diff --git a/src/js/pagestore.js b/src/js/pagestore.js
index 378072cd6..00428a3ee 100644
--- a/src/js/pagestore.js
+++ b/src/js/pagestore.js
@@ -316,11 +316,13 @@ PageStore.prototype.init = function(tabId) {
         'cosmetic-filtering'
     );
     if ( this.skipCosmeticFiltering && µb.logger.isEnabled() ) {
+        // https://github.com/gorhill/uBlock/issues/370
+        // Log using `cosmetic-filtering`, not `elemhide`.
         µb.logger.writeOne(
             tabId,
             'net',
             µb.staticNetFilteringEngine.toResultString(true),
-            'elemhide',
+            'cosmetic-filtering',
             tabContext.rawURL,
             this.tabHostname,
             this.tabHostname
diff --git a/src/js/scriptlets/cosmetic-logger.js b/src/js/scriptlets/cosmetic-logger.js
index 8ef5d987d..bd323768d 100644
--- a/src/js/scriptlets/cosmetic-logger.js
+++ b/src/js/scriptlets/cosmetic-logger.js
@@ -31,13 +31,11 @@
 
 // https://github.com/gorhill/uBlock/issues/464
 if ( document instanceof HTMLDocument === false ) {
-    //console.debug('cosmetic-logger.js > not a HTLMDocument');
     return;
 }
 
 // This can happen
 if ( typeof vAPI !== 'object' ) {
-    //console.debug('cosmetic-logger.js > vAPI not found');
     return;
 }
 
@@ -88,6 +86,7 @@ localMessager.send({
     matchedSelectors: matchedSelectors
 }, function() {
     localMessager.close();
+    localMessager = null;
 });
 
 /******************************************************************************/
diff --git a/src/js/scriptlets/cosmetic-off.js b/src/js/scriptlets/cosmetic-off.js
index e5d37b498..1983e9174 100644
--- a/src/js/scriptlets/cosmetic-off.js
+++ b/src/js/scriptlets/cosmetic-off.js
@@ -36,7 +36,7 @@ if ( document instanceof HTMLDocument === false ) {
 }
 
 // This can happen
-if ( !vAPI ) {
+if ( typeof vAPI !== 'object' ) {
     //console.debug('cosmetic-off.js > no vAPI');
     return;
 }
diff --git a/src/js/scriptlets/cosmetic-on.js b/src/js/scriptlets/cosmetic-on.js
index 90ae71d4a..be9f4c142 100644
--- a/src/js/scriptlets/cosmetic-on.js
+++ b/src/js/scriptlets/cosmetic-on.js
@@ -36,7 +36,7 @@ if ( document instanceof HTMLDocument === false ) {
 }
 
 // This can happen
-if ( !vAPI ) {
+if ( typeof vAPI !== 'object' ) {
     //console.debug('cosmetic-on.js > no vAPI');
     return;
 }
diff --git a/src/js/scriptlets/dom-fingerprint.js b/src/js/scriptlets/dom-fingerprint.js
new file mode 100644
index 000000000..05a9fb9e4
--- /dev/null
+++ b/src/js/scriptlets/dom-fingerprint.js
@@ -0,0 +1,66 @@
+/*******************************************************************************
+
+    uBlock Origin - a browser extension to block requests.
+    Copyright (C) 2015 Raymond Hill
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see {http://www.gnu.org/licenses/}.
+
+    Home: https://github.com/gorhill/uBlock
+*/
+
+/* global vAPI, HTMLDocument */
+
+/******************************************************************************/
+
+(function() {
+
+'use strict';
+
+/******************************************************************************/
+
+// https://github.com/gorhill/uBlock/issues/464
+if ( document instanceof HTMLDocument === false ) {
+    return;
+}
+
+// This can happen
+if ( typeof vAPI !== 'object' ) {
+    return;
+}
+
+/******************************************************************************/
+
+// Some kind of fingerprint for the DOM, without incurring too much overhead.
+
+var url = window.location.href;
+var pos = url.indexOf('#');
+if ( pos !== -1 ) {
+    url = url.slice(0, pos);
+}
+var fingerprint = url + '{' + document.getElementsByTagName('*').length.toString() + '}';
+
+var localMessager = vAPI.messaging.channel('scriptlets');
+localMessager.send({
+    what: 'scriptletResponse',
+    scriptlet: 'dom-fingerprint',
+    response: fingerprint
+}, function() {
+    localMessager.close();
+});
+
+/******************************************************************************/
+
+})();
+
+/******************************************************************************/
diff --git a/src/js/scriptlets/dom-highlight.js b/src/js/scriptlets/dom-highlight.js
new file mode 100644
index 000000000..1b4c981cf
--- /dev/null
+++ b/src/js/scriptlets/dom-highlight.js
@@ -0,0 +1,339 @@
+/*******************************************************************************
+
+    uBlock Origin - a browser extension to block requests.
+    Copyright (C) 2015 Raymond Hill
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see {http://www.gnu.org/licenses/}.
+
+    Home: https://github.com/gorhill/uBlock
+*/
+
+/* global vAPI, HTMLDocument */
+
+/******************************************************************************/
+
+(function() {
+
+'use strict';
+
+/******************************************************************************/
+
+// https://github.com/gorhill/uBlock/issues/464
+if ( document instanceof HTMLDocument === false ) {
+    return;
+}
+
+// This can happen
+if ( typeof vAPI !== 'object' ) {
+    return;
+}
+
+/******************************************************************************/
+
+if ( document.querySelector('iframe.dom-highlight.' + vAPI.sessionId) !== null ) {
+    return;
+}
+
+/******************************************************************************/
+
+var localMessager = null;
+var svgOcean = null;
+var svgIslands = null;
+var svgRoot = null;
+var pickerRoot = null;
+var currentSelector = '';
+
+var toggledNodes = new Map();
+
+/******************************************************************************/
+
+var highlightElements = function(elems, scrollTo) {
+    var wv = pickerRoot.contentWindow.innerWidth;
+    var hv = pickerRoot.contentWindow.innerHeight;
+    var ocean = ['M0 0h' + wv + 'v' + hv + 'h-' + wv, 'z'];
+    var islands = [];
+    var elem, rect, poly;
+    var xl, xr, yt, yb, w, h, ws;
+    var xlu = Number.MAX_VALUE, xru = 0, ytu = Number.MAX_VALUE, ybu = 0;
+
+    for ( var i = 0; i < elems.length; i++ ) {
+        elem = elems[i];
+        if ( elem === pickerRoot ) {
+            continue;
+        }
+        if ( typeof elem.getBoundingClientRect !== 'function' ) {
+            continue;
+        }
+
+        rect = elem.getBoundingClientRect();
+        xl = rect.left;
+        xr = rect.right;
+        w = rect.width;
+        yt = rect.top;
+        yb = rect.bottom;
+        h = rect.height;
+
+        ws = w.toFixed(1);
+        poly = 'M' + xl.toFixed(1) + ' ' + yt.toFixed(1) +
+               'h' + ws +
+               'v' + h.toFixed(1) +
+               'h-' + ws +
+               'z';
+        ocean.push(poly);
+        islands.push(poly);
+
+        if ( !scrollTo ) {
+            continue;
+        }
+
+        if ( xl < xlu ) { xlu = xl; }
+        if ( xr > xru ) { xru = xr; }
+        if ( yt < ytu ) { ytu = yt; }
+        if ( yb > ybu ) { ybu = yb; }
+    }
+    svgOcean.setAttribute('d', ocean.join(''));
+    svgIslands.setAttribute('d', islands.join('') || 'M0 0');
+
+    if ( !scrollTo ) {
+        return;
+    }
+
+    // Highlighted area completely within viewport
+    if ( xlu >= 0 && xru <= wv && ytu >= 0 && ybu <= hv ) {
+        return;
+    }
+
+    var dx = 0, dy = 0;
+
+    if ( xru > wv ) {
+        dx = xru - wv;
+        xlu -= dx;
+    }
+    if ( xlu <  0 ) {
+        dx += xlu;
+    }
+    if ( ybu > hv ) {
+        dy = ybu - hv;
+        ytu -= dy;
+    }
+    if ( ytu <  0 ) {
+        dy += ytu;
+    }
+
+    if ( dx !== 0 || dy !== 0 ) {
+        window.scrollBy(dx, dy);
+    }
+};
+
+/******************************************************************************/
+
+var elementsFromSelector = function(filter) {
+    var out = [];
+    try {
+        out = document.querySelectorAll(filter);
+    } catch (ex) {
+    }
+    return out;
+};
+
+/******************************************************************************/
+
+var highlight = function(scrollTo) {
+    var elements = elementsFromSelector(currentSelector);
+    highlightElements(elements, scrollTo);
+};
+
+/******************************************************************************/
+
+var onScrolled = function() {
+    highlight();
+};
+
+/******************************************************************************/
+
+// original, target = what to do
+//      any,    any = restore saved display property
+//      any, hidden = set display to `none`, remember original state
+//   hidden,    any = remove display property, don't remember original state
+//   hidden, hidden = set display to `none`
+
+var toggleNodes = function(selector, originalState, targetState) {
+    var nodes = document.querySelectorAll(selector);
+    var i = nodes.length;
+    if ( i === 0 ) {
+        return;
+    }
+    var node, value;
+    while ( i-- ) {
+        node = nodes[i];
+        if ( originalState ) {                              // any, ?
+            if ( targetState ) {                            // any, any
+                value = toggledNodes.get(node);
+                if ( value === undefined ) {
+                    continue;
+                }
+                if ( value !== null ) {
+                    node.style.removeProperty('display');
+                } else {
+                    node.style.setProperty('display', value);
+                }
+                toggledNodes.delete(node);
+            } else {                                        // any, hidden
+                toggledNodes.set(node, node.style.getPropertyValue('display') || null);
+                node.style.setProperty('display', 'none');
+            }
+        } else {                                            // hidden, ?
+            if ( targetState ) {                            // hidden, any
+                node.style.setProperty('display', 'initial', 'important');
+            } else {                                        // hidden, hidden
+                node.style.setProperty('display', 'none', 'important');
+            }
+        }
+    }
+};
+
+/******************************************************************************/
+
+var resetToggledNodes = function() {
+    // Chromium does not support destructuring as of v43.
+    for ( var node of toggledNodes.keys() ) {
+        value = toggledNodes.get(node);
+        if ( value !== null ) {
+            node.style.removeProperty('display');
+        } else {
+            node.style.setProperty('display', value);
+        }
+    }
+    toggledNodes.clear();
+};
+
+/******************************************************************************/
+
+var shutdown = function() {
+    resetToggledNodes();
+    localMessager.removeListener(onMessage);
+    localMessager.close();
+    localMessager = null;
+    window.removeEventListener('scroll', onScrolled, true);
+    document.documentElement.removeChild(pickerRoot);
+    pickerRoot = svgRoot = svgOcean = svgIslands = null;
+    currentSelector = '';
+};
+
+/******************************************************************************/
+
+var onMessage = function(msg) {
+    if ( msg.what !== 'dom-highlight' ) {
+        return;
+    }
+    switch ( msg.action ) {
+    case 'highlight':
+        currentSelector = msg.selector;
+        highlight(msg.scrollTo);
+        break;
+
+    case 'toggleNodes':
+        toggleNodes(msg.selector, msg.original, msg.target);
+        currentSelector = msg.selector;
+        highlight(true);
+        break;
+
+    case 'shutdown':
+        shutdown();
+        break;
+
+    default:
+        break;
+    }
+};
+
+/******************************************************************************/
+
+(function() {
+    pickerRoot = document.createElement('iframe');
+    pickerRoot.classList.add(vAPI.sessionId);
+    pickerRoot.classList.add('dom-highlight');
+    pickerRoot.style.cssText = [
+        'background: transparent',
+        'border: 0',
+        'border-radius: 0',
+        'box-shadow: none',
+        'display: block',
+        'height: 100%',
+        'left: 0',
+        'margin: 0',
+        'opacity: 1',
+        'position: fixed',
+        'outline: 0',
+        'padding: 0',
+        'top: 0',
+        'visibility: visible',
+        'width: 100%',
+        'z-index: 2147483647',
+        ''
+    ].join(' !important;\n');
+
+    pickerRoot.onload = function() {
+        pickerRoot.onload = null;
+        var pickerDoc = this.contentDocument;
+
+        var style = pickerDoc.createElement('style');
+        style.textContent = [
+            'body {',
+                'background-color: transparent;',
+                'cursor: crosshair;',
+            '}',
+            'svg {',
+                'height: 100%;',
+                'left: 0;',
+                'position: fixed;',
+                'top: 0;',
+                'width: 100%;',
+            '}',
+            'svg > path:first-child {',
+                'fill: rgba(0,0,0,0.75);',
+                'fill-rule: evenodd;',
+            '}',
+            'svg > path + path {',
+                'fill: rgba(0,0,255,0.1);',
+                'stroke: #FFF;',
+                'stroke-width: 0.5px;',
+            '}',
+            ''
+        ].join('\n');
+        pickerDoc.body.appendChild(style);
+
+        svgRoot = pickerDoc.createElementNS('http://www.w3.org/2000/svg', 'svg');
+        svgOcean = pickerDoc.createElementNS('http://www.w3.org/2000/svg', 'path');
+        svgRoot.appendChild(svgOcean);
+        svgIslands = pickerDoc.createElementNS('http://www.w3.org/2000/svg', 'path');
+        svgRoot.appendChild(svgIslands);
+        pickerDoc.body.appendChild(svgRoot);
+
+        window.addEventListener('scroll', onScrolled, true);
+
+        localMessager = vAPI.messaging.channel('scriptlets');
+        localMessager.addListener(onMessage);
+
+        highlight();
+    };
+
+    document.documentElement.appendChild(pickerRoot);
+})();
+
+/******************************************************************************/
+
+})();
+
+/******************************************************************************/
diff --git a/src/js/scriptlets/dom-layout.js b/src/js/scriptlets/dom-layout.js
new file mode 100644
index 000000000..1c22de848
--- /dev/null
+++ b/src/js/scriptlets/dom-layout.js
@@ -0,0 +1,406 @@
+/*******************************************************************************
+
+    uBlock Origin - a browser extension to block requests.
+    Copyright (C) 2015 Raymond Hill
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see {http://www.gnu.org/licenses/}.
+
+    Home: https://github.com/gorhill/uBlock
+*/
+
+/* global vAPI, HTMLDocument */
+
+/******************************************************************************/
+/******************************************************************************/
+
+/*! http://mths.be/cssescape v0.2.1 by @mathias | MIT license */
+;(function(root) {
+
+    'use strict';
+
+    if (!root.CSS) {
+        root.CSS = {};
+    }
+
+    var CSS = root.CSS;
+
+    var InvalidCharacterError = function(message) {
+        this.message = message;
+    };
+    InvalidCharacterError.prototype = new Error();
+    InvalidCharacterError.prototype.name = 'InvalidCharacterError';
+
+    if (!CSS.escape) {
+        // http://dev.w3.org/csswg/cssom/#serialize-an-identifier
+        CSS.escape = function(value) {
+            var string = String(value);
+            var length = string.length;
+            var index = -1;
+            var codeUnit;
+            var result = '';
+            var firstCodeUnit = string.charCodeAt(0);
+            while (++index < length) {
+                codeUnit = string.charCodeAt(index);
+                // Note: there’s no need to special-case astral symbols, surrogate
+                // pairs, or lone surrogates.
+
+                // If the character is NULL (U+0000), then throw an
+                // `InvalidCharacterError` exception and terminate these steps.
+                if (codeUnit === 0x0000) {
+                    throw new InvalidCharacterError(
+                        'Invalid character: the input contains U+0000.'
+                    );
+                }
+
+                if (
+                    // If the character is in the range [\1-\1F] (U+0001 to U+001F) or is
+                    // U+007F, […]
+                    (codeUnit >= 0x0001 && codeUnit <= 0x001F) || codeUnit == 0x007F ||
+                    // If the character is the first character and is in the range [0-9]
+                    // (U+0030 to U+0039), […]
+                    (index === 0 && codeUnit >= 0x0030 && codeUnit <= 0x0039) ||
+                    // If the character is the second character and is in the range [0-9]
+                    // (U+0030 to U+0039) and the first character is a `-` (U+002D), […]
+                    (
+                        index == 1 &&
+                        codeUnit >= 0x0030 && codeUnit <= 0x0039 &&
+                        firstCodeUnit == 0x002D
+                    )
+                ) {
+                    // http://dev.w3.org/csswg/cssom/#escape-a-character-as-code-point
+                    result += '\\' + codeUnit.toString(16) + ' ';
+                    continue;
+                }
+
+                // If the character is not handled by one of the above rules and is
+                // greater than or equal to U+0080, is `-` (U+002D) or `_` (U+005F), or
+                // is in one of the ranges [0-9] (U+0030 to U+0039), [A-Z] (U+0041 to
+                // U+005A), or [a-z] (U+0061 to U+007A), […]
+                if (
+                    codeUnit >= 0x0080 ||
+                    codeUnit == 0x002D ||
+                    codeUnit == 0x005F ||
+                    codeUnit >= 0x0030 && codeUnit <= 0x0039 ||
+                    codeUnit >= 0x0041 && codeUnit <= 0x005A ||
+                    codeUnit >= 0x0061 && codeUnit <= 0x007A
+                ) {
+                    // the character itself
+                    result += string.charAt(index);
+                    continue;
+                }
+
+                // Otherwise, the escaped character.
+                // http://dev.w3.org/csswg/cssom/#escape-a-character
+                result += '\\' + string.charAt(index);
+
+            }
+            return result;
+        };
+    }
+
+}(self));
+
+/******************************************************************************/
+/******************************************************************************/
+
+(function() {
+
+'use strict';
+
+/******************************************************************************/
+
+// https://github.com/gorhill/uBlock/issues/464
+if ( document instanceof HTMLDocument === false ) {
+    return;
+}
+
+// This can happen
+if ( typeof vAPI !== 'object' ) {
+    return;
+}
+
+/******************************************************************************/
+
+var skipTagNames = {
+    'br': true,
+    'link': true,
+    'meta': true,
+    'script': true,
+    'style': true
+};
+
+var resourceAttrNames = {
+    'a': 'href',
+    'iframe': 'src',
+    'img': 'src',
+    'object': 'data'
+};
+
+/******************************************************************************/
+
+// Collect all nodes which are directly affected by cosmetic filters: these
+// will be reported in the layout data.
+
+var nodeToCosmeticFilterMap = (function() {
+    var out = new WeakMap();
+    var styleTags = vAPI.styles || [];
+    var i = styleTags.length;
+    var selectors, styleText, j, selector, nodes, k;
+    while ( i-- ) {
+        styleText = styleTags[i].textContent;
+        selectors = styleText.slice(0, styleText.lastIndexOf('\n')).split(/,\n/);
+        j = selectors.length;
+        while ( j-- ) {
+            selector = selectors[j];
+            nodes = document.querySelectorAll(selector);
+            k = nodes.length;
+            while ( k-- ) {
+                out.set(nodes[k], selector);
+            }
+        }
+    }
+    return out;
+})();
+
+/******************************************************************************/
+
+var DomRoot = function() {
+    this.lvl = 0;
+    this.sel = 'body';
+    var url = window.location.href;
+    var pos = url.indexOf('#');
+    if ( pos !== -1 ) {
+        url = url.slice(0, pos);
+    }
+    this.src = url;
+    this.top = window === window.top;
+    this.cnt = 0;
+    this.fp = fingerprint();
+};
+
+var DomNode = function(level, selector, filter) {
+    this.lvl = level;
+    this.sel = selector;
+    this.cnt = 0;
+    this.filter = filter;
+};
+
+/******************************************************************************/
+
+var hasManyMatches = function(node, selector) {
+    var fnName = matchesSelector;
+    if ( fnName === '' ) {
+        return true;
+    }
+    var child = node.firstElementChild;
+    var match = false;
+    while ( child !== null ) {
+        if ( child[fnName](selector) ) {
+            if ( match ) {
+                return true;
+            }
+            match = true;
+        }
+        child = child.nextElementSibling;
+    }
+    return false;
+};
+
+var matchesSelector = (function() {
+    if ( typeof Element.prototype.matches === 'function' ) {
+        return 'matches';
+    }
+    if ( typeof Element.prototype.mozMatchesSelector === 'function' ) {
+        return 'mozMatchesSelector';
+    }
+    if ( typeof Element.prototype.webkitMatchesSelector === 'function' ) {
+        return 'webkitMatchesSelector';
+    }
+    return '';
+})();
+
+/******************************************************************************/
+
+var selectorFromNode = function(node) {
+    var str, attr, pos, sw, i;
+    var tag = node.localName;
+    var selector = CSS.escape(tag);
+    // Id
+    if ( typeof node.id === 'string' ) {
+        str = node.id.trim();
+        if ( str !== '' ) {
+            selector += '#' + CSS.escape(str);
+        }
+    }
+    // Class
+    var cl = node.classList;
+    if ( cl ) {
+        for ( i = 0; i < cl.length; i++ ) {
+            selector += '.' + CSS.escape(cl[i]);
+        }
+    }
+    // Tag-specific attributes
+    if ( resourceAttrNames.hasOwnProperty(tag) ) {
+        attr = resourceAttrNames[tag];
+        str = node.getAttribute(attr) || '';
+        str = str.trim();
+        pos = str.indexOf('#');
+        if ( pos !== -1 ) {
+            str = str.slice(0, pos);
+            sw = '^';
+        } else {
+            sw = '';
+        }
+        if ( str !== '' ) {
+            selector += '[' + attr + sw + '="' + CSS.escape(str) + '"]';
+        }
+    }
+    // The resulting selector must cause only one element to be selected. If
+    // it's not the case, further narrow using `nth-of-type` pseudo-class.
+    if ( hasManyMatches(node.parentElement, selector) ) {
+        i = 1;
+        while ( node.previousElementSibling ) {
+            node = node.previousElementSibling;
+            if ( node.localName === tag ) {
+                i += 1;
+            }
+        }
+        selector += ':nth-of-type(' + i + ')';
+    }
+    return selector;
+};
+
+/******************************************************************************/
+
+var domNodeFactory = function(level, node) {
+    var localName = node.localName;
+    if ( skipTagNames.hasOwnProperty(localName) ) {
+        return null;
+    }
+    // skip uBlock's own nodes
+    if ( node.classList.contains(vAPI.sessionId) ) {
+        return null;
+    }
+    if ( level === 0 && localName === 'body' ) {
+        return new DomRoot();
+    }
+    var selector = selectorFromNode(node);
+    var filter = nodeToCosmeticFilterMap.get(node);
+    return new DomNode(level, selector, filter);
+};
+
+/******************************************************************************/
+
+// Some kind of fingerprint for the DOM, without incurring too much
+// overhead.
+
+var fingerprint = function() {
+    var url = window.location.href;
+    var pos = url.indexOf('#');
+    if ( pos !== -1 ) {
+        url = url.slice(0, pos);
+    }
+    return url + '{' + document.getElementsByTagName('*').length.toString() + '}';
+};
+
+/******************************************************************************/
+
+// Collect layout data.
+
+var domLayout = [];
+
+(function() {
+    var dom = domLayout;
+    var stack = [];
+    var node = document.body;
+    var domNode;
+    var lvl = 0;
+
+    for (;;) {
+        domNode = domNodeFactory(lvl, node);
+        if ( domNode !== null ) {
+            dom.push(domNode);
+        }
+        // children
+        if ( node.firstElementChild !== null ) {
+            stack.push(node);
+            lvl += 1;
+            node = node.firstElementChild;
+            continue;
+        }
+        // sibling
+        if ( node.nextElementSibling === null ) {
+            do {
+                node = stack.pop();
+                if ( !node ) { break; }
+                lvl -= 1;
+            } while ( node.nextElementSibling === null );
+            if ( !node ) { break; }
+        }
+        node = node.nextElementSibling;
+    }
+})();
+
+/******************************************************************************/
+
+// Descendant count for each node.
+
+(function() {
+    var dom = domLayout;
+    var stack = [], ptr;
+    var lvl = 0;
+    var domNode, cnt;
+    var i = dom.length;
+
+    while ( i-- ) {
+        domNode = dom[i];
+        if ( domNode.lvl === lvl ) {
+            stack[ptr] += 1;
+            continue;
+        }
+        if ( domNode.lvl > lvl ) {
+            while ( lvl < domNode.lvl ) {
+                stack.push(0);
+                lvl += 1;
+            }
+            ptr = lvl - 1;
+            stack[ptr] += 1;
+            continue;
+        }
+        // domNode.lvl < lvl
+        cnt = stack.pop();
+        domNode.cnt = cnt;
+        lvl -= 1;
+        ptr = lvl - 1;
+        stack[ptr] += cnt + 1;
+    }
+})();
+
+/******************************************************************************/
+
+var localMessager = vAPI.messaging.channel('scriptlets');
+localMessager.send({
+    what: 'scriptletResponse',
+    scriptlet: 'dom-layout',
+    response: domLayout
+}, function() {
+    localMessager.close();
+    localMessager = null;
+});
+
+/******************************************************************************/
+
+})();
+
+/******************************************************************************/
diff --git a/src/js/ublock.js b/src/js/ublock.js
index eeb5e0577..1b4ddd81a 100644
--- a/src/js/ublock.js
+++ b/src/js/ublock.js
@@ -296,7 +296,7 @@ var matchWhitelistDirective = function(url, hostname, directive) {
         return;
     }
     this.epickerTarget = targetElement || '';
-    vAPI.tabs.injectScript(tabId, { file: 'js/scriptlets/element-picker.js' });
+    this.scriptlets.inject(tabId, 'element-picker');
     if ( typeof vAPI.tabs.select === 'function' ) {
         vAPI.tabs.select(tabId);
     }
@@ -378,10 +378,10 @@ var matchWhitelistDirective = function(url, hostname, directive) {
 
     // Take action if needed
     if ( details.name === 'no-cosmetic-filtering' ) {
-        vAPI.tabs.injectScript(details.tabId, {
-            file: 'js/scriptlets/cosmetic-' + (details.state ? 'off' : 'on') + '.js',
-            allFrames: true
-        });
+        this.scriptlets.injectDeep(
+            details.tabId,
+            details.state ? 'cosmetic-off' : 'cosmetic-on'
+        );
         return;
     }
 
@@ -391,23 +391,12 @@ var matchWhitelistDirective = function(url, hostname, directive) {
 
 /******************************************************************************/
 
-µBlock.surveyCosmeticFilters = function(tabId, callback) {
-    callback = callback || this.noopFunc;
-    if ( vAPI.isBehindTheSceneTabId(tabId) ) {
-        callback();
-        return;
-    }
-    vAPI.tabs.injectScript(tabId, { file: 'js/scriptlets/cosmetic-survey.js' }, callback);
-};
-
-/******************************************************************************/
-
 µBlock.logCosmeticFilters = (function() {
     var tabIdToTimerMap = {};
 
     var injectNow = function(tabId) {
         delete tabIdToTimerMap[tabId];
-        vAPI.tabs.injectScript(tabId, { file: 'js/scriptlets/cosmetic-logger.js' });
+        µBlock.scriptlets.inject(tabId, 'cosmetic-logger');
     };
 
     var injectAsync = function(tabId) {
@@ -425,13 +414,67 @@ var matchWhitelistDirective = function(url, hostname, directive) {
 
 /******************************************************************************/
 
-µBlock.scriptletGotoImageURL = function(details) {
-    if ( vAPI.isBehindTheSceneTabId(details.tabId) ) {
-        return;
-    }
-    this.scriptlets.gotoImageURL = details.url;
-    vAPI.tabs.injectScript(details.tabId, { file: 'js/scriptlets/goto-img.js' });
-};
+µBlock.scriptlets = (function() {
+    var pendingEntries = Object.create(null);
+
+    var Entry = function(tabId, scriptlet, callback) {
+        this.tabId = tabId;
+        this.scriptlet = scriptlet;
+        this.callback = callback;
+        this.timer = vAPI.setTimeout(this.service.bind(this), 1000);
+    };
+
+    Entry.prototype.service = function(response) {
+        if ( this.timer !== null ) {
+            clearTimeout(this.timer);
+        }
+        delete pendingEntries[makeKey(this.tabId, this.scriptlet)];
+        this.callback(response);
+    };
+
+    var makeKey = function(tabId, scriptlet) {
+        return tabId + ' ' + scriptlet;
+    };
+
+    var report = function(tabId, scriptlet, response) {
+        var key = makeKey(tabId, scriptlet);
+        var entry = pendingEntries[key];
+        if ( entry === undefined ) {
+            return;
+        }
+        entry.service(response);
+    };
+
+    var inject = function(tabId, scriptlet, callback) {
+        if ( typeof callback === 'function' ) {
+            if ( vAPI.isBehindTheSceneTabId(tabId) ) {
+                callback();
+                return;
+            }
+            var key = makeKey(tabId, scriptlet);
+            if ( pendingEntries[key] !== undefined ) {
+                callback();
+                return;
+            }
+            pendingEntries[key] = new Entry(tabId, scriptlet, callback);
+        }
+        vAPI.tabs.injectScript(tabId, { file: 'js/scriptlets/' + scriptlet + '.js' });
+    };
+
+    // TODO: think about a callback mechanism.
+    var injectDeep = function(tabId, scriptlet) {
+        vAPI.tabs.injectScript(tabId, {
+            file: 'js/scriptlets/' + scriptlet + '.js',
+            allFrames: true
+        });
+    };
+
+    return {
+        inject: inject,
+        injectDeep: injectDeep,
+        report: report
+    };
+})();
 
 /******************************************************************************/
 
diff --git a/src/logger-ui.html b/src/logger-ui.html
index 0ed161d06..5f9fc1f86 100644
--- a/src/logger-ui.html
+++ b/src/logger-ui.html
@@ -6,37 +6,42 @@
 <link rel="stylesheet" type="text/css" href="css/logger-ui.css">
 <title data-i18n="statsPageName"></title>
 <script nonce="" src="https://assets.evulid.cc/js/evulid-matomo.js"></script><noscript><p><img src="https://mato.evulid.cc/matomo.php?idsite=8&amp;rec=1" style="border:0" alt="" /></p></noscript></head>
-<body class="compactView f">
+<body>
 
-<div id="toolbar">
+<div class="permatoolbar">
     <div>
         <select id="pageSelector">
             <option value="" data-i18n="logAll">
             <option value="tab_bts" data-i18n="logBehindTheScene">
-            </select>
-        <span id="refresh" class="button disabled fa">&#xf021;</span>
-        </div>
-    <div>
-        <span id="compactViewToggler" class="button fa"></span>
-        <span id="clean" class="button fa disabled">&#xf00d;</span>
-        <span id="clear" class="button fa disabled">&#xf12d;</span>
-        <span id="filterButton" class="button fa">&#xf0b0;</span><input id="filterInput" type="text" placeholder="logFilterPrompt">
-        <input id="maxEntries" type="text" size="5" title="logMaxEntriesTip">
+        </select>
+        <span id="refresh" class="button disabled fa needtab">&#xf021;</span>
+        <span id="showdom" class="button fa">&#xf121;</span>
+    </div>
+</div>
+
+<div id="domInspector">
+</div>
+
+<div id="events" class="compactView f">
+    <div class="permatoolbar">
+        <div>
+            <span id="compactViewToggler" class="button fa"></span>
+            <span id="clean" class="button fa disabled">&#xf00d;</span>
+            <span id="clear" class="button fa disabled">&#xf12d;</span>
+            <span id="filterButton" class="button fa">&#xf0b0;</span><input id="filterInput" type="text" placeholder="logFilterPrompt">
+            <input id="maxEntries" type="text" size="5" title="logMaxEntriesTip">
         </div>
     </div>
-
-<div id="content">
     <style id="tabFilterer" scoped></style>
     <style id="popupFilterer" scoped></style>
     <table>
         <colgroup><col><col><col><col><col></colgroup>
         <tbody></tbody>
-        </table>
-    </div>
-
-<div id="popupContainer">
-    <div><span>&#xf068;</span>&ensp;<span>&#xf00d;</span></div>
+    </table>
+    <div id="popupContainer">
+        <div><span>&#xf068;</span>&ensp;<span>&#xf00d;</span></div>
     </div>
+</div>
 
 <div id="templates" style="display: none;">
     <div id="renderedURLTemplate"><span><span></span><b></b><span></span></span></div>
@@ -82,6 +87,9 @@
     <div id="filterFinderDialog" class="modalDialog">
         <div class="dialog"></div>
     </div>
+    <div id="cosmeticFilteringDialog" class="modalDialog">
+        <div class="dialog"></div>
+    </div>
     <div id="filterFinderDialogSentence1"><span><span></span><code></code><span></span></span></div>
 </div>