Developer Tools

by Zulkarnain K.

50 Add-ons in this Collection

Firebug by Joe Hewitt, Jan Odvarko, others

Rated 4 out of 5 stars 2,116 reviews

1,809,250 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 877 reviews

419,624 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.

JavaScript Debugger by James Ross, Robert Ginda, others

Rated 4 out of 5 stars 49 reviews

105,084 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.

Web Developer by chrispederick

Rated 5 out of 5 stars 262 reviews

415,746 users

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

SQLite Manager by lazierthanthou

Rated 4 out of 5 stars 70 reviews

184,642 users

Manage any SQLite database on your computer.

Tamper Data by Adam Judson

Rated 4 out of 5 stars 147 reviews

94,836 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 375 reviews

225,966 users

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

Lightbeam for Firefox by Mozilla

Rated 4 out of 5 stars 441 reviews

380,624 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.

JavaScript Deobfuscator by Wladimir Palant

Rated 5 out of 5 stars 20 reviews

45,816 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.

Live HTTP Headers by Daniel Savard, Nikolas Co

Rated 4 out of 5 stars 173 reviews

126,272 users

View HTTP headers of a page and while browsing.

JSONView by Ben Hollis

Rated 5 out of 5 stars 177 reviews

108,255 users

View JSON documents in the browser.

HttpFox by Martin Theimer

Rated 4 out of 5 stars 172 reviews

75,144 users

An HTTP analyzer addon for Firefox

Remote XUL Manager by Jorge Villalobos

Rated 5 out of 5 stars 37 reviews

73,304 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 72 reviews

106,887 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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