Lightning Requires Restart Featured

Organize your schedule and life's important events in a calendar that's fully integrated with your Thunderbird email. Manage multiple calendars, create your daily to do list, invite friends to events, and subscribe to public calendars.

Rated 3 out of 5 stars (1,922)
22,603 weekly downloads

Session Manager

Session Manager saves and restores the state of all or some windows - either when you want it or automatically at startup and after crashes. It can also automatically save the state of open windows individually.

Rated 4 out of 5 stars (486)
7,337 weekly downloads

QuickNote Requires Restart

A simple note-taking extension.

Rated 5 out of 5 stars (174)
4,229 weekly downloads

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 (227)
4,222 weekly downloads

Add-ons Manager Context Menu Requires Restart

Add more items to Add-ons Manager context menu.

Rated 5 out of 5 stars (37)
4,111 weekly downloads


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 (229)
3,472 weekly downloads

Unpacked extension loader Requires Restart

This addon should be useful for addon developers who prefer to work with unpacked exentsions for test purpose.

Rated 4 out of 5 stars (2)
2,586 weekly downloads

ChatZilla Requires Restart

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

Rated 4 out of 5 stars (125)
2,244 weekly downloads

Diagnostics for Adblock Plus

Diagnostics tool for Adblock Plus, provides some insight into internal processes of Adblock Plus.

Not yet rated
2,161 weekly downloads

Send Later Requires Restart

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

Rated 5 out of 5 stars (79)
2,049 weekly downloads


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.

Rated 4 out of 5 stars (328)
1,929 weekly downloads

Copy Plain Text 2 Requires Restart

Copies text without formatting

Rated 5 out of 5 stars (69)
1,411 weekly downloads


Lets the user direct the submission of a form to a new tab or window. [Bug #17754]

Rated 5 out of 5 stars (14)
1,226 weekly downloads

Mail Redirect Requires Restart

Allow to redirect (a.k.a. "remail") mail messages to other recipients.

Rated 4 out of 5 stars (131)
1,181 weekly downloads

Copy As Plain Text Requires Restart

Removes formatting from copied text.

Rated 4 out of 5 stars (59)
1,101 weekly downloads

Extension Auto-Installer

Extension Auto-Installer is a helper for Firefox/SeaMonkey/Thunderbird extension developers: it allows automatically adding or updating browser extensions, e.g. via command line tools. This makes testing your changes easier.

Rated 5 out of 5 stars (16)
823 weekly downloads

Mouse Gestures Suite Requires Restart

Mouse gestures for SeaMonkey & Firefox: navigate & execute commands using mouse gestures (with single mouse button) and rocker gestures (by pressing 2 mouse buttons). Also: scroll wheel navigation, page scrolling, tab scrolling.

Rated 4 out of 5 stars (39)
739 weekly downloads

PlayFlash 32bit Requires Restart

Flash player plugin - unofficial xpi repack for 32bit browsers.
Use when official plugin installer is not suitable.
All binary files are copyrighted by their authors and distributed for free.

Rated 5 out of 5 stars (6)
656 weekly downloads

AutoProxy-ng Requires Restart

This is a fork of AutoProxy, which can run the latest version of Firefox.

Rated 4 out of 5 stars (15)
645 weekly downloads

Filter Uploader for Adblock Plus (unofficial) Requires Restart

DOES NOT BLOCK ADS! Don't install this add-on if you don't know what 'uploading' means!

This add-on Uploads the filters from your Adblock Plus installation to a FTP, HTTP, HTTPS server...

Rated 4 out of 5 stars (40)
644 weekly downloads