Most Popular Extensions

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Mozilla Archive Format, with MHT and Faithful Save Requires Restart

— Open web pages saved with Internet Explorer or other browsers (MHT)
— Save many tabs, video and audio reliably, in a single ZIP file (MAFF)
— Return to the original site you saved a page from, and more!

Rated 5 out of 5 stars (352)
70,506 users

Send Later Requires Restart

True "Send Later" functionality to schedule the time for sending an email.

Rated 5 out of 5 stars (114)
66,531 users

Image Zoom Requires Restart

Adds zoom and rotation functionality for images...

Rated 4 out of 5 stars (353)
66,044 users

UnMHT

UnMHT allows you to view MHT (MHTML) web archive format files, and save complete web pages, including text and graphics, into a single MHT file in Firefox/SeaMonkey.

Rated 4 out of 5 stars (295)
64,395 users

µBlock

The most efficient blocker for Firefox.

No ads, no tracking, and insanely faster page loads.

Rated 4 out of 5 stars (248)
61,159 users

Mail Merge Requires Restart

Mass Mail and Personal Mail

Rated 5 out of 5 stars (157)
58,112 users

LookOut (fix version) Requires Restart

LookOut is a plugin which allows Thunderbird to interface with Microsoft's mail tools by decoding metadata and attachments encapsulated/embedded in a TNEF encoded attachment (aka winmail.dat).
Support: Thunderbird and SeaMonkey

Rated 4 out of 5 stars (22)
58,020 users

Saved Password Editor Requires Restart

Adds the ability to create and edit entries in the password manager.

Rated 5 out of 5 stars (384)
56,955 users

JavaScript Debugger Requires Restart

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 (52)
56,813 users

ChatZilla Requires Restart

A clean, easy to use and highly extensible Internet Relay Chat (IRC) client.

Rated 4 out of 5 stars (146)
54,334 users

DOM Inspector Requires Restart

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.

Rated 5 out of 5 stars (77)
54,281 users

Add-ons Manager Context Menu Requires Restart

Add more items to Add-ons Manager context menu.

Rated 5 out of 5 stars (48)
54,217 users

RefControl Requires Restart

Control what gets sent as the HTTP Referer on a per-site basis.

Rated 4 out of 5 stars (180)
53,881 users

VKontakte.ru Downloader (music/videos/photos @ VK) Requires Restart

Download music, videos and photos from VK.com / vkontakte.ru. One-click download, natural filenames, displaying file size and bitrate for music, downloading HD video, downloading HQ photos. No spam, no usage of your account, no spyware.

Rated 4 out of 5 stars (512)
53,677 users

InlineDisposition

InlineDisposition changes the disposition of Content-Disposition response headers from attachment to inline; this prevents servers from forcing the browser to save a file and allows that file to be viewed in the browser, if the browser supports it.

Rated 5 out of 5 stars (48)
50,635 users

Proxy Tool Requires Restart

Proxy Tool - Powerful, yet User-friendly proxy tool to manage your proxies and anonymity needs, including: 46M+ user agents (world's largest), 10 different spoofed HTTP referrers, auto-proxy rotation, plus many more. Developed by http://ProxyList.co

Rated 3 out of 5 stars (48)
47,641 users

Youtube MP3 Podcaster Requires Restart

Self contained add-on for downloading youtube videos to mp3 for easy listening on podcasting gadgets like a Zune or iPod

Rated 4 out of 5 stars (269)
47,128 users

Thumbnail Zoom Plus Requires Restart

Shows full image when you hover over a thumbnail. Works with Amazon, Baidu Images, Bing Images, Facebook, Flickr, Google+, Google Images, IMDb, LinkedIn, Netflix, Pinterest, Reddit, Twitter, Yandex, YouTube, Wikipedia, Yahoo Images, & many more.

Rated 4 out of 5 stars (393)
42,282 users

IE View Requires Restart

Lets you load pages in IE with a single right-click, or mark certain sites to *always* load in IE.

Rated 3 out of 5 stars (155)
40,109 users

Bluhell Firewall

Get a faster browsing experience by blocking nasty web resources using Bluhell Firewall, the lightweight Ad-Blocker and Tracking/Privacy Protector.

Rated 4 out of 5 stars (495)
38,319 users