Most Popular Extensions
Add-ons Manager Context Menu Requires Restart
Add more items to Add-ons Manager context menu.
MinimizeToTray revived Requires Restart
Minimizes windows into the system tray.
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)
Image Zoom Requires Restart
Adds zoom and rotation functionality for images...
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.
Text Link Requires Restart
Allows URI texts written in webpages to be loaded by double clicks.
gContactSync Requires Restart
Synchronizes contacts & groups between Thunderbird or SeaMonkey and Google Contacts. Imports Facebook friends, contacts you follow on Twitter, and more.
Quicktext Requires Restart
Quicktext is an extension for Thunderbird that lets you create templates that can be easily inserted into your own emails.
By blocking annoying ads and nosy trackers, adaware ad block nearly doubles your browsing speed! And with the most robust antivirus-level cloud-scanning technology of any ad blocker on the market, you’ll be safe from the latest cyber-threats.
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.
As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.
Saved Password Editor Requires Restart
Adds the ability to create and edit entries in the password manager.
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.
Signature Switch Requires Restart
Switch the signature on/off or choose a new one from your predefined set...
Get a faster browsing experience by blocking nasty web resources using Bluhell Firewall, the lightweight Ad-Blocker and Tracking/Privacy Protector.
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).
Send Later Requires Restart
True "Send Later" functionality to schedule the time for sending an email.
Mail Merge Requires Restart Featured
Mass Mail and Personal Mail
Ad Blocker lets you block all ads, tracking & malware from the web world. It is an effective solution to browse the web without offensive and annoying ads you hate to see.
KeeFox Requires Restart
Simple and secure password management. Login automatically, never forget another password, stay in control of your passwords and improve their security. Powered by the world-renowned KeePass Password Safe.