Most Popular Extensions
Text2Link Requires Restart
Text2Link is a simple and easy-to-use way to copy the text of a link, or to open URLs and send emails to addresses not marked-up as HTML links.
User Agent Switcher Requires Restart
The User Agent Switcher extension adds a menu and a toolbar button to switch the user agent of a browser.
Show contact photo and other info from Local Dir, Addressbook, LDAP, Facebook, LinkedIn, Flickr, Gravatar etc
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.
Gmail Manager NG Requires Restart
Based on Gmail Manager by Todd Long. This fork is intended to a supported version of Gmail Manager since Todd appears to have gone MIA. Manage multiple Gmail accounts and receive new mail notifications.
Zindus Requires Restart
Google and Zimbra contact sync for Thunderbird. (TB 24 and above NOT supported)
LookOut+ Requires Restart
LookOut is a plugin which allows to interface with Microsoft's mail tools by decoding metadata and attachments encapsulated/embedded in a TNEF encoded attachment (aka winmail.dat).
This version is a fix for Seamonkey 2.*.
Use SeaMonkey as a standalone e-mail client. Set up a default browser for links opened from Mail & Newsgroups.
SQLite Manager Requires Restart
Manage any SQLite database on your computer.
Complete YouTube Saver Requires Restart
Download YouTube videos in various formats including 1080p, 4K etc (DASH formats). Convert audio track from videos to MP3 or WAV, or save audio in native format (Ogg, AAC/M4A, MP3, OPUS). Save YouTube page, video, comments and subtitles to one folder
Auto delete cookies, localStorage and IndexedDB objects as soon as they become unused
If you are the kind of person who likes to have total control over every aspect of your downloads, "Download Status Bar" is the add-on you are looking for.
Spanish (Spain) ChatZilla Requires Restart
Spanish (es-ES) Language Pack for ChatZilla
Year view Requires Restart
Year view for calendar.
QuickNote Requires Restart
A simple note-taking extension.
This extension makes browsing for extensions easier at addons.mozilla.org. It fixes incorrect information about some extensions being not available for SeaMonkey and adds links to the Add-on Converter where needed.
Send Filter Requires Restart
This add-on allows you run your message filters automatically on outgoing messages after sending. In other words, it's a outgoing filter for thunderbird and seamonkey.
Adds icons to buttons and/or menus.
Contact Photos Requires Restart
Displays contact photos in the message header.
This extension provides various customization options for the Adblock Plus user interface.