The Web Developer extension adds various web developer tools to the browser.
FireFTP is a free, secure, cross-platform FTP/SFTP client for Mozilla Firefox which provides easy and intuitive access to FTP/SFTP servers.
Check out my new project, FireSSH!
Advanced Eyedropper, Color Picker, Gradient Generator and other colorful goodies...
Firefox OS Simulator is a test environment for Firefox OS. Use it to test your apps in a Firefox OS-like environment that looks and feels like a mobile phone. After installing it, go to Web Developer > Firefox OS Simulator to access its features.
Draw a ruler across any webpage to check the width, height, or alignment of page elements in pixels.
Debug Flash/SWF files on the web. Edit properties and inspect elements on the fly. View log output inside the extension. Run AS3 code against the active SWF. Access assets with the Explorer. View AMF calls and Shared Objects and much much more...
Wappalyzer is a browser extension that identifies software on websites.
Color tools for web development.
Color picker and eyedropper + saving colors and trying out colors with drag and drop.
HTML Validator is a Mozilla extension that adds HTML validation inside Firefox and Mozilla. The number of errors of a HTML page is seen on the form of an icon
For Firefox 23+, you need 0.958 (under review)
Show the IP address(es) of the current page in the status bar. It also allows querying custom information services by IP (right click) and hostname (left click), like whois, netcraft, etc. Additionally you can copy the IP address to the clipboard.
A must have tool for Web Developers and Testers to Manage and monitor web cookies.
Export / Backup
Import / Restore
Available in English, French, Spanish, German and Italian languages.
FontFinder is created for designers, developers and typographers. It allows a user to analyze the font information of any element on a page, copy any piece(s) of that information to the clipboard, and perform inline replacements to test new layouts.