Lightning 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 (1,874)
47,756 weekly downloads

µBlock No Restart

Finally, an efficient blocker. Easy on CPU and memory.

Rated 4 out of 5 stars (209)
18,610 weekly downloads

Session Manager No Restart

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 (567)
7,769 weekly downloads


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 (202)
4,848 weekly downloads

Copy Plain Text 2

Copies text without formatting

Rated 5 out of 5 stars (61)
4,730 weekly downloads

UnMHT No Restart

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 (217)
3,336 weekly downloads

Add-ons Manager Context Menu

Add more items to Add-ons Manager context menu.

Rated 5 out of 5 stars (32)
3,070 weekly downloads


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

Rated 4 out of 5 stars (126)
2,778 weekly downloads


A simple note-taking extension.

Rated 5 out of 5 stars (169)
2,093 weekly downloads

Copy As Plain Text

Removes formatting from copied text.

Rated 4 out of 5 stars (56)
1,781 weekly downloads

Snap Links Plus

Select a number of links with a rectangle and open them all in new tabs in the same or a new window(s), download them or copy them to the clipboard. You can also lasso checkboxes to quickly check or uncheck them.

Rated 4 out of 5 stars (97)
1,679 weekly downloads

Send Later

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

Rated 5 out of 5 stars (39)
1,581 weekly downloads

Filter Uploader for Adblock Plus

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 3 out of 5 stars (45)
1,559 weekly downloads

FoxClocks No Restart

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 (311)
1,246 weekly downloads

Extension Auto-Installer No Restart

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 (13)
953 weekly downloads

Mail Redirect

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

Rated 4 out of 5 stars (124)
944 weekly downloads

AutoPager Fixed

AutoPager Fixed is a working version of AutoPager extension for Firefox 36+ (non-E10s mode) to autoload the next page(s) when you scroll pages.


Rated 4 out of 5 stars (44)
924 weekly downloads

Mouse Gestures Suite

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 (22)
865 weekly downloads

Add-ons Button No Restart

Opens the Add-ons window to perform tasks on your installed Extensions, Themes, Plug-ins and Language packs.

Rated 5 out of 5 stars (1)
782 weekly downloads

AutoCopy 2

Copies selected text to the clipboard automatically.

Rated 5 out of 5 stars (57)
729 weekly downloads