Developer Tools

by Zulkarnain K.

50 Add-ons in this Collection

Firebug by Joe Hewitt, Jan Odvarko, others

Rated 4 out of 5 stars 2,088 reviews

1,933,422 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 863 reviews

435,371 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 260 reviews

439,234 users

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

Lightbeam for Firefox by Mozilla

Rated 4 out of 5 stars 435 reviews

394,526 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.

SQLite Manager by lazierthanthou

Rated 4 out of 5 stars 68 reviews

192,828 users

Manage any SQLite database on your computer.

ColorZilla by Alex Sirota

Rated 4 out of 5 stars 343 reviews

241,255 users

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

Tamper Data by Adam Judson

Rated 4 out of 5 stars 145 reviews

99,332 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.

Live HTTP Headers by Daniel Savard, Nikolas Co

Rated 4 out of 5 stars 172 reviews

134,210 users

View HTTP headers of a page and while browsing.

JavaScript Debugger by James Ross, Robert Ginda, others

Rated 4 out of 5 stars 49 reviews

106,662 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.

JSONView by Ben Hollis

Rated 5 out of 5 stars 176 reviews

113,214 users

View JSON documents in the browser.

HttpFox by Martin Theimer

Rated 4 out of 5 stars 172 reviews

79,347 users

An HTTP analyzer addon for Firefox

JavaScript Deobfuscator by Wladimir Palant

Rated 5 out of 5 stars 20 reviews

46,924 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

67,521 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 127 reviews

30,325 users

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