Most Popular Extensions

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Quick Locale Switcher Requires Restart

Allows you to quickly switch to a different language (User Interface, Spell Checker Dictionary and Website content) in your Mozilla application.

Rated 3 out of 5 stars (88)
142,643 users

Image Zoom Requires Restart

Adds zoom and rotation functionality for images...

Rated 4 out of 5 stars (341)
136,336 users

Text Link Requires Restart

Allows URI texts written in webpages to be loaded by double clicks.

Rated 4 out of 5 stars (296)
123,548 users

CompactHeader Requires Restart Featured

Add symbol in header plane to switch between compact and expanded view. Options to switch between one or two lines compact view, which buttons should be displayed in header pane. For Thunderbird 36 and older use version 2.0.9 (see version history)

Rated 5 out of 5 stars (172)
120,925 users

Manually sort folders Requires Restart

This extension allows you to manually sort (order) your folders in the folder pane of Thunderbird or automatically sort them, but in a better way. This extension also allows you to re-order accounts in the folder pane.

Rated 4 out of 5 stars (130)
117,217 users

Extra Folder Columns Requires Restart

This extension is for those TB3 users who want the multiple-columns view that TB2 allowed

IMPORTANT: If you are using Thunderbird 38 or later, uninstall this addon. The functionality is in core now.

Rated 4 out of 5 stars (248)
114,411 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 (69)
112,476 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 5 out of 5 stars (287)
111,218 users

Toolbar Buttons

Adds toolbar buttons to the customize toolbar window in several programs including Firefox, Thunderbird and SeaMonkey. Some of the buttons make commonly preformed actions quicker, others add new functionality.

Rated 4 out of 5 stars (324)
105,294 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 (50)
103,804 users

Theme Font & Size Changer

Theme Font & Size Changer lets you change the global font size and font family used for the user interface in Firefox. Design your browser with your favorite font.

Rated 5 out of 5 stars (169)
93,825 users

X-notifier (for Gmail,Hotmail,Yahoo,AOL ...) Requires Restart

Notifier for gmail, yahoo, hotmail, aol and more webmails.
X-notifier(aka WebMail Notifier) checks your webmail accounts and notifies the number of unread emails...
Supports : gmail, yahoo, hotmail, POP3/IMAP, facebook, twitter and more

Rated 4 out of 5 stars (1,695)
87,897 users

Saved Password Editor Requires Restart

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

Rated 5 out of 5 stars (230)
85,955 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 5 out of 5 stars (227)
85,763 users

Quicktext Requires Restart

Quicktext is an extension for Thunderbird that lets you create templates that can be easily inserted into your own emails.

Rated 4 out of 5 stars (332)
81,072 users

Signature Switch Requires Restart

Switch the signature on/off or choose a new one from your predefined set...

Rated 4 out of 5 stars (180)
76,381 users

HTML5 Video Everywhere!

Replace video player with Firefox native video player

Rated 4 out of 5 stars (38)
74,731 users

ReminderFox Requires Restart

ReminderFox displays and manages lists of reminders and ToDo's. ReminderFox makes sure you remember all of your important dates via easy-to-use lists, alerts, and alarms, right in your browser without the need for a separate calendar program.

Rated 4 out of 5 stars (527)
72,970 users

gContactSync Requires Restart

Synchronizes contacts & groups between Thunderbird or SeaMonkey and Google Contacts. Imports Facebook friends, contacts you follow on Twitter, and more.

Rated 4 out of 5 stars (221)
72,266 users

Remove Duplicate Messages (Alternate) Requires Restart

Search and remove messages which are the same as other messages in your mail folders (referred to as duplicates or dupes).

Rated 4 out of 5 stars (147)
61,306 users