Both Chrome DevTools and Firefox DevTools support extensions. Some of the popular extension: * React Devtools, Ember Inspector, AngularJS Batarang, Backbone DevTools, Knockout.js context debugger, and many other JS-framework specific extensions. * RailsPanel, Django Debug Panel, and a dozen of extensions for PHP frameworks. * Three.js Editor (https://github.com/spite/ThreeJSEditorExtension) Developer documentation: * https://developer.chrome.com/extensions/devtools https://developer.mozilla.org/en-US/Add-ons/Setting_up_extension_development_environment * https://developer.mozilla.org/en-US/docs/Tools#Extending_the_devtools
<rdar://problem/24356072>
<rdar://problem/9276565>
*** Bug 156608 has been marked as a duplicate of this bug. ***