Developer Tools

by Zulkarnain K.

50 Add-ons in this Collection

Firebug by Joe Hewitt, Jan Odvarko, others

Rated 4 out of 5 stars 2,082 reviews

1,715,509 users

Firebug integrates with Firefox to put a wealth of development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page...

Stylish by userstyles.org

Rated 4 out of 5 stars 827 reviews

400,090 users

Restyle the web with Stylish, a user styles manager. Stylish lets you easily install themes and skins for Google, Facebook, YouTube, Tumblr, and many, many other sites. You can even customize Firefox and other programs themselves.

Web Developer by chrispederick

Rated 5 out of 5 stars 265 reviews

391,854 users

The Web Developer extension adds various web developer tools to the browser.

SQLite Manager by lazierthanthou

Rated 4 out of 5 stars 77 reviews

180,144 users

Manage any SQLite database on your computer.

Tamper Data by Adam Judson

Rated 4 out of 5 stars 153 reviews

91,444 users

Use tamperdata to view and modify HTTP/HTTPS headers and post parameters...

RESTClient, a debugger for RESTful web services. by Chao ZHOU

Notice: some important features (XML indentation and load old saved requests) are missing in version 2.0.0, please update to version 2.0.1.

Please follow the link ("View other versions") below To install version 2.0.1.

ColorZilla by Alex Sirota

Rated 4 out of 5 stars 378 reviews

214,239 users

Advanced Eyedropper, Color Picker, Gradient Generator and other colorful goodies...

JavaScript Debugger by James Ross, Robert Ginda, others

Rated 4 out of 5 stars 50 reviews

105,397 users

As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.

Venkman is the code name for Mozilla's JavaScript Debugger. Venkman aimed to provide a powerful JavaScript debugging environment for Mozilla based browsers.

Lightbeam for Firefox by Mozilla

Rated 4 out of 5 stars 431 reviews

339,388 users

Lightbeam is a Firefox add-on that enables you to see the first and third party sites you interact with on the Web. Using interactive visualizations, Lightbeam shows you the relationships between these third parties and the sites you visit.

Live HTTP Headers by Daniel Savard, Nikolas Co

Rated 4 out of 5 stars 171 reviews

120,075 users

View HTTP headers of a page and while browsing.

HttpFox by Martin Theimer

Rated 4 out of 5 stars 172 reviews

72,816 users

An HTTP analyzer addon for Firefox

JSONView by Ben Hollis

Rated 5 out of 5 stars 176 reviews

106,513 users

View JSON documents in the browser.

JavaScript Deobfuscator by Wladimir Palant

Rated 5 out of 5 stars 22 reviews

44,108 users

This add-on shows you what JavaScript code runs on a web page, even if it is obfuscated and generated on the fly. Simply open JavaScript Deobfuscator from the Web Developer menu and watch the scripts being compiled/executed.

Remote XUL Manager by Jorge Villalobos

Rated 5 out of 5 stars 37 reviews

83,594 users

Manages the Remote XUL whitelist to allow websites and local files to load XUL content. For versions compatible with Firefox 41 and lower, see All Versions page below.

about:addons-memory by Nils Maier

Download Now

Experimental

Rated 4 out of 5 stars 129 reviews

27,515 users

Adds an about:addons-memory page that details add-on memory usage
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