Extensions by Weekly Downloads
Font Finder Requires Restart
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.
ExQuilla for Microsoft Exchange Requires Restart
Thunderbird email accounts connecting to Microsoft Exchange Web Services. A 60 day trial of a paid add-on.
Update for Thunderbird 52: See https://exquilla.zendesk.com/hc/en-us/articles/115001708463. Summary: estimated on 2017-04-23 or try beta.
Google Docs Viewer (PDF, DOCX, PPTX, XLSX, etc...) Requires Restart
View publicly-accessible PDF, DOCX, PPTX, XLSX, among other files online with Google Docs by only 2 clicks. Click as usual for your default viewer. Support bookmarked URLs. Security and your explicit viewing intention are always honored.
Master Password+ Requires Restart
Various enhancements for build-in "master password" (MP)
-Locks master security device on demand or after specified time
-Prompts for MP on browser startup
-Suppresses all or duplicate MP prompts
-Locks up entire application or individual windows
'Classic Toolbar Buttons' add-on restores old toolbar button ui (known from Fx 4-7s small view, Fx 4-12s large view & Tb 5-14) for current Firefox, Thunderbird and Seamonkey versions.
Beta builds on versions page!
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
Simple Locale Switcher Requires Restart
An easier management of the user interface language
Saved Password Editor Requires Restart
Adds the ability to create and edit entries in the password manager.
FireTray Requires Restart
A system tray extension for Linux and Windows, allowing to set up custom icon, hiding to tray instead of closing, display the number of unread messages in mailing applications, and other features ...
FoxyProxy Basic Requires Restart
FoxyProxy Basic is a simple on/off proxy switcher. More advanced features and configuration options are offered by FoxyProxy Standard.
Copy Plain Text 2 Requires Restart
Copies text without formatting
"Restart" menu and button, with configurable shortcut key.
Quicktext Requires Restart
Quicktext is an extension for Thunderbird that lets you create templates that can be easily inserted into your own emails.
Website Blocker Requires Restart
Block websites you don't want the browser to get into.
Block by a whole domain name or a specific address.
Block until further notice or until a certain date.
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.
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.
Diagnostics tool for Adblock Plus, provides some insight into internal processes of Adblock Plus.
FoxClocks shows times around the world - or just your local time - at the bottom of your browser. It deals with daylight saving time so you don't have to.
ProfileSwitcher Requires Restart
It adds some options to launch easily other profiles and the Profile Manager.
This addon provides a conversation view for Thunderbird, grouping messages together and allowing you to reply "inline" thus providing a more efficient workflow.
The latest version is compatible with Thunderbird 38+ only (see below for details).