Use Redux DevTools in the DevTools
Custom Style Script
Click on any HTML element to get the font info in a popup
Picture in Play
Indicates whether the `picture` element is in use on a page.
Firebug Lite for Opera 15+
PDF API HTML5
Browse JSON like you do it in Finder.
Browserling - Cross-browser testing
Cross-browser test websites in the most popular browsers such as Internet Explorer, Edge, Chrome, Firefox, Safari and Opera. Try for free!
This extension allows you to add your own custom website specific CSS style sheets.
View all HTTP Requests and Responses sent between the Web browser and the Web server.
Live HTTP Headers
Monitor all HTTP/HTTPs traffic from your browser.
Live editor for CSS and LESS - Magic CSS
Live preview of CSS/LESS code with an in-page editor. Autocomplete, convert LESS to CSS, beautify, minify, CSS reloader, linter, ...
Wayback machine website
Online service that have 452 billion web pages saved over time and who is domain tool in context menu
Quickly view the HTTP headers of the current tab.
WordPress Theme and Plugins Detector
This tool detects theme and plugins used on WordPress sites and displays information about them.
Website Analysis & SEO Tool
Website SEO audit tool that provides website analysis in SEO, performance, validity, security, accessibility and other criteria.
Edit the Page
Toggles the 'Design Mode' so that you can edit the contents of the page.
Remove cookie(s) for the current domain
Remove cookie(s) for the current site with just one click
Nextsense XML Signing Component
Signing XML document.
ChroPath for Opera
AutonomIQ offers a developers platform ChroPath to generate and validate unique selectors like relative xpath with iframe support
An extention to show/inspect and analyze fonts in web-pages.
A browser extension that brings a new GitHub experience
Right Click Validator
Right click on any webpage to validate it using the W3 NUValidator service.
Shows the response times and uptime of a desired server. Useful to see how performs internet or a wireless access point.
Google Analytics Debugger
A browser extension for debugging Google Analytics tracking code
Corser - Authorize CORS requests
Cross-browser extension for authorizing cross-origin resource sharing (CORS) requests. This extension can be installed on browsers supporting the WebExtensions API (https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions) It intercepts all CORS requests and responses headers, and records/adds/changes their values so as to authorized unauthorized CORS requests. Use this extension only for testing purposes
Get Thumbnails or Image to video YouTube
Make thumbnail previews or images from YouTube videos
A small extension to validate the markup of current tab
Internet users feedback about the sites