Developer Tools

by Zulkarnain K.

50 Add-ons in this Collection

Firebug by Joe Hewitt, Jan Odvarko, others

Rated 4 out of 5 stars 2,634 reviews

879,487 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 - Custom themes for any website by userstyles.org

Rated 4 out of 5 stars 1,279 reviews

323,997 users

Stylish lets you customize any website with custom user styles (themes for websites). Choose from the largest userstyles library to change the color scheme, background, and skin for Google, Facebook, YouTube and many, many more sites.

Web Developer by chrispederick

Rated 4 out of 5 stars 472 reviews

266,777 users

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

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

RESTClient has been completely rewritten for compatible with Firefox 57. Some functions are still missing (OAuth & OAuth 2.0 authentication).

ColorZilla by Alex Sirota

Rated 4 out of 5 stars 428 reviews

178,591 users

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

Tamper Data by Adam Judson

Rated 4 out of 5 stars 305 reviews

47,374 users

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

SQLite Manager by lazierthanthou

Rated 4 out of 5 stars 313 reviews

108,956 users

Manage any SQLite database on your computer.

Firefox Lightbeam by Mozilla

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 214 reviews

70,424 users

View HTTP headers of a page and while browsing.

HttpFox by Martin Theimer

Rated 4 out of 5 stars 205 reviews

39,416 users

An HTTP analyzer addon for Firefox

Remote XUL Manager by Jorge Villalobos

Rated 5 out of 5 stars 36 reviews

89,195 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.

JavaScript Debugger by James Ross, Robert Ginda, others

Rated 4 out of 5 stars 50 reviews

60,899 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 194 reviews

57,458 users

View JSON documents in the browser.

XPather by Viktor Zigo

Rated 4 out of 5 stars 34 reviews

652 users

Feature rich XPath generator, editor, inspector and simple extraction tool...

JavaScript Deobfuscator by Wladimir Palant

Rated 5 out of 5 stars 26 reviews

21,880 users

Important note: This extension will not work in Firefox 57 and above. Providing this functionality in Firefox is no longer possible, the extension is discontinued.
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