Miscellaneous

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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 (1,921)
5,617,494 users

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 (481)
273,196 users

ChatZilla Requires Restart

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

Rated 4 out of 5 stars (125)
122,788 users

UnMHT

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 (227)
88,459 users

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 (221)
76,373 users

Send Later Requires Restart

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

Rated 5 out of 5 stars (76)
62,214 users

FoxClocks

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 (327)
62,017 users

Copy Plain Text 2 Requires Restart

Copies text without formatting

Rated 5 out of 5 stars (66)
44,013 users

Diagnostics for Adblock Plus

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

Not yet rated
37,119 users

Mail Redirect Requires Restart

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

Rated 4 out of 5 stars (129)
34,748 users

QuickNote Requires Restart

A simple note-taking extension.

Rated 5 out of 5 stars (173)
26,659 users

Copy As Plain Text Requires Restart

Removes formatting from copied text.

Rated 4 out of 5 stars (59)
20,288 users

SmartTemplate4 Requires Restart

SmartTemplate4 offers an easy way to automatically create customized replies by auto-inserting various mail headers. Templates can be created for every account as well as for the default (all email accounts). Also supports the Stationery Add-on.

Rated 5 out of 5 stars (51)
19,583 users

AutoCopy 2 Requires Restart

Copies selected text to the clipboard automatically.

Rated 5 out of 5 stars (65)
18,267 users

Add-ons Manager Context Menu Requires Restart

Add more items to Add-ons Manager context menu.

Rated 5 out of 5 stars (35)
18,024 users

Filter Uploader for Adblock Plus 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)
15,697 users

Quote Colors Requires Restart

Quote Colors allows you to select text and background colors of different quote levels which are applied when reading or printing mail/news messages. Additionally, you can choose between graphical and traditional plain text quoting display mode.

Rated 4 out of 5 stars (44)
14,012 users

MinimizeToTray Plus Requires Restart

Note from Mozilla: This add-on has been discontinued. Try MinimizeToTray Revived instead.

Minimize applications to the system tray.

Rated 4 out of 5 stars (193)
12,567 users

Add-on Update Checker Requires Restart

Adds Tools menu item to check Add-ons for updates. Includes toolbar icon.

Rated 4 out of 5 stars (54)
12,492 users

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 (36)
12,486 users