Selenium IDE Requires Restart
Selenium IDE is an integrated development environment for Selenium tests. It is implemented as a Firefox extension, and allows you to record, edit, and debug tests.
ipFood Requires Restart Featured
Simulate the use of a series of proxy changing at each new connection.
RequestPolicy Requires Restart
Be in control of which cross-site requests are allowed. Improve the privacy of your browsing by not letting other sites know your browsing habits. Secure yourself from Cross-Site Request Forgery (CSRF) and other attacks.
HttpRequester Requires Restart
A tool for easily making HTTP requests (GET/PUT/POST/DELETE), viewing the responses, and keeping a history of transactions.
Wappalyzer is a browser extension that identifies software on websites.
Emoji Cheatsheet Featured
A reference for the codes to generate Emojis on popular sites like GitHub or Basecamp and Unicode characters for Twitter and Facebook.
Search Emojis by name or view recently selected items. Emojis are automatically copied to the clipboard.
Override browser user agent string
Pearl Crescent Page Saver screenshot tool Requires Restart
Save an image of a web page (including Flash content) to a file. Web page screenshots may be captured interactively or from the command line. Options allow you to control the output format (PNG or JPEG), image file name, scaling, and much more.
WebRTC leaks your actual IP addresses from behind your VPN, by default.
FirePath Requires Restart
FirePath is a Firebug extension that adds a development tool to edit, inspect and generate XPath 1.0 expressions, CSS 3 selectors and JQuery selectors (Sizzle selector engine).
CacheViewer Requires Restart
This extenion is GUI Front-end of "about:cache"...
A very simple extension for learning web page colors. Copy the RGB or Hex color code of any pixel displayed in your browser to the clipboard (in CSS/HTML format). Similar in function to Internet Explorer's color picker.
User-Agent Switcher Featured
Quickly and easily switch between popular user-agent strings.
HttpFox Requires Restart
An HTTP analyzer addon for Firefox
IE Tab + (FF 8+, 7, 6, 5, 4, 3.6, 3.5, SeaMonkey) Requires Restart
IE Tab + is an enhanced version of IE Tab. It supports FF 3.5 or greater, integrates IE Tab with Adblock Plus in the IE Tab engine, and synchronizes cookies between IE and Firefox. You can easily import settings from the original IE Tab into IE Tab +
Accelerate your SEO efforts on the fly. SEOquake is a free plugin for browsers that provides you with key SEO metrics for a specific page, along with other useful tools such as SEO Audit and many others.
Autofill Forms Requires Restart
Autofill Forms enables you to fill out web forms with one click.
YSlow Requires Restart
YSlow analyzes web pages and suggests ways to improve their performance based on a set of rules for high performance web pages.
http://yslow.org is the official open source website.
URL Fixer Plus RU and UA Requires Restart
Extended URL Fixer for RU and UA
JS Print Setup Requires Restart