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Live HTTP Headers (clone) No Restart

View HTTP headers of a page and while browsing.

This is an unofficial "Live HTTP headers" clone, mainly to fix the Replay feature!

Rated 5 out of 5 stars (3)
2,337 users

Remote XUL Manager No Restart

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.

Rated 5 out of 5 stars (36)
77,339 users

Sharp Color Picker No Restart

A full featured color selector tool, to work with colors, and easily find the colors you want.

Rated 4 out of 5 stars (1)
2,219 users

jQuery

jQuery and jQuery UI embedded in browser

Rated 4 out of 5 stars (7)
2,844 users

about:addons-memory 2016 No Restart

Adds a new page that shows add-on memory usage

Rated 5 out of 5 stars (18)
6,795 users

Live HTTP Headers (Fixed By ITWorld.com.pk)

View HTTP headers of a page and while browsing.
Live HTTP Header Fix By Danyial ITs Working On Firefox Again Fixed Reply Problem

Rated 4 out of 5 stars (5)
2,212 users

JSONovich No Restart

Pretty-prints JSON content in the browser for easy, unobtrusive viewing.

Rated 4 out of 5 stars (36)
9,822 users

Element Inspector No Restart

In the DOM Inspector,quickly navigate to the any elements

Rated 5 out of 5 stars (28)
3,544 users

HttpFox

An HTTP analyzer addon for Firefox

Rated 4 out of 5 stars (168)
88,886 users

Font Finder

FontFinder is created for designers, developers and typographers. It allows a user to analyze the font information of any element on a page, copy any piece(s) of that information to the clipboard, and perform inline replacements to test new layouts.

Rated 4 out of 5 stars (71)
35,918 users

Cookie Exporter

Exports all cookies in IE manner.
Makes a Netscape standard cookies.txt file.
Very useful for WGET --load-cookies option.

Rated 5 out of 5 stars (13)
4,805 users

Full Web Page Screenshots (♥♥♥♥♥)

FireShot makes full web page screenshots. Demo: http://bit.ly/RlBQMV

Screenshots can be quickly captured and:

― Saved as Image or PDF
― Sent to clipboard
― Printed
― Annotated *
― Uploaded *
― E-Mailed *

* OS Windows only

Rated 5 out of 5 stars (452)
284,747 users

Firesizer

Allows you to resize the window to specific dimensions.

NOTE: Users of Firefox 29 and above must install "The Addon Bar" extension to use this, as Firesizer uses the add-on bar that has been removed in Firefox 29.

Rated 4 out of 5 stars (129)
27,033 users

Add-ons Manager - Version Number No Restart

Restores version numbers for all installed add-ons inside Add-on Manager on Firefox, Thunderbird and Seamonkey.

Rated 5 out of 5 stars (18)
1,591 users

Browser View Plus

Open links, pages, and bookmarks in any other browser or media player. Modify any menu, browser name or location. Incognito/private browsing mode is also supported. Works for all Firefox locales/languages.

Rated 5 out of 5 stars (20)
1,055 users

Cookie Importer

Imports cookies from a textfile.
Reads Netscape standard cookies.txt files as exported by IE and others.
Very useful in combination with the Cookie Exporter add-on.

Rated 5 out of 5 stars (2)
7,127 users

Tiny JavaScript Debugger

TinyJSD is a JavaScript debugger for privileged code running Mozilla products like Firefox, Thunderbird, SeaMonkey. It serves to debug the application as well as extensions written in JavaScript.

Rated 4 out of 5 stars (6)
36,713 users

Copy Pure Text

Allows to copy selected text as plain text by adding a 'Copy as Text' menu item to context menu.

Rated 4 out of 5 stars (15)
3,796 users

Web Developer

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

Rated 5 out of 5 stars (235)
478,687 users

JavaScript Debugger

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.

Rated 4 out of 5 stars (50)
114,054 users