Developer Tools

by Zulkarnain K.

50 Add-ons in this Collection

Firebug by Joe Hewitt, Jan Odvarko, others

Rated 4 out of 5 stars 2,696 reviews

760,794 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...

Tamper Data by Adam Judson

Rated 4 out of 5 stars 327 reviews

39,345 users

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

Stylish - Custom themes for any website by userstyles.org

Rated 4 out of 5 stars 1,313 reviews

305,624 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 491 reviews

248,348 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 443 reviews

170,976 users

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

SQLite Manager by lazierthanthou

Rated 4 out of 5 stars 340 reviews

96,152 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.

JSONView by Ben Hollis

Rated 5 out of 5 stars 197 reviews

52,475 users

View JSON documents in the browser.

HttpFox by Martin Theimer

Rated 4 out of 5 stars 211 reviews

34,626 users

An HTTP analyzer addon for Firefox

Live HTTP Headers by Daniel Savard, Nikolas Co

Rated 4 out of 5 stars 216 reviews

60,718 users

View HTTP headers of a page and while browsing.

Remote XUL Manager by Jorge Villalobos

Rated 5 out of 5 stars 36 reviews

95,827 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 52 reviews

53,673 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.

JavaScript Deobfuscator by Wladimir Palant

Rated 5 out of 5 stars 26 reviews

18,868 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.

XPather by Viktor Zigo

Rated 4 out of 5 stars 34 reviews

574 users

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