Developer Tools

by Zulkarnain K.

51 Add-ons in this Collection

Firebug by Joe Hewitt, Jan Odvarko, others

Rated 5 out of 5 stars 1,840 reviews

2,018,974 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

Rated 4 out of 5 stars 834 reviews

449,363 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 248 reviews

447,456 users

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

SQLite Manager by lazierthanthou

Rated 4 out of 5 stars 58 reviews

189,595 users

Manage any SQLite database on your computer.

Tamper Data by Adam Judson

Rated 4 out of 5 stars 142 reviews

100,557 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.

Lightbeam for Firefox by Mozilla

Rated 4 out of 5 stars 423 reviews

426,770 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.

ColorZilla by Alex Sirota

Rated 5 out of 5 stars 311 reviews

247,864 users

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

Live HTTP Headers by Daniel Savard, Nikolas Co

Rated 4 out of 5 stars 170 reviews

138,335 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

108,506 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 168 reviews

109,178 users

View JSON documents in the browser.

HttpFox by Martin Theimer

Rated 4 out of 5 stars 170 reviews

80,993 users

An HTTP analyzer addon for Firefox

JavaScript Deobfuscator by Wladimir Palant

Rated 5 out of 5 stars 20 reviews

48,843 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 36 reviews

76,988 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.

DOM Inspector by SeaMonkey Council

Rated 5 out of 5 stars 70 reviews

118,577 users

DOM Inspector is a tool that can be used to inspect and edit the live DOM of any web document or XUL application. The DOM can be navigated using a two-paned window displaying a variety of different views on the document and all nodes within.
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