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 (1,884)
10,613 weekly downloads

µBlock No Restart

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

Rated 4 out of 5 stars (215)
8,455 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 5 out of 5 stars (437)
2,445 weekly downloads

Copy Plain Text 2

Copies text without formatting

Rated 5 out of 5 stars (64)
1,596 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 (205)
1,386 weekly downloads

Add-ons Manager Context Menu

Add more items to Add-ons Manager context menu.

Rated 5 out of 5 stars (32)
1,086 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 (220)
1,014 weekly downloads


A simple note-taking extension.

Rated 5 out of 5 stars (169)
993 weekly downloads


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

Rated 4 out of 5 stars (126)
939 weekly downloads

Copy As Plain Text

Removes formatting from copied text.

Rated 4 out of 5 stars (56)
580 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)
479 weekly downloads

Send Later

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

Rated 5 out of 5 stars (41)
466 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)
444 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 (15)
438 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 (314)
422 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 (47)
285 weekly downloads

Tab notifier

Enables desktop notifications like in Chrome (e.g. Gmail, imo.im) and, if the site doesn't support them, it can notify new messages or updates detecting changes of the title (e.g. Hotmail, Yahoo, Facebook, Twitter). Even if the browser is minimized!

Rated 4 out of 5 stars (40)
243 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 5 out of 5 stars (25)
240 weekly downloads

Mail Redirect

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

Rated 4 out of 5 stars (125)
237 weekly downloads

AutoCopy 2

Copies selected text to the clipboard automatically.

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