Most Popular Extensions
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.
Image Zoom Requires Restart
Adds zoom and rotation functionality for images...
Text Link Requires Restart
Allows URI texts written in webpages to be loaded by double clicks.
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)
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.
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.
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.
Get a faster browsing experience by blocking nasty web resources using Bluhell Firewall, the lightweight Ad-Blocker and Tracking/Privacy Protector.
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.
As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.
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.
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
Saved Password Editor Requires Restart
Adds the ability to create and edit entries in the password manager.
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.
Quicktext Requires Restart
Quicktext is an extension for Thunderbird that lets you create templates that can be easily inserted into your own emails.
Signature Switch Requires Restart
Switch the signature on/off or choose a new one from your predefined set...
Replace video player with Firefox native video player
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.
gContactSync Requires Restart
Synchronizes contacts & groups between Thunderbird or SeaMonkey and Google Contacts. Imports Facebook friends, contacts you follow on Twitter, and more.