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 (1,830)
6,344,574 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 (460)
276,827 users

Add-ons Manager Context Menu Requires Restart

Add more items to Add-ons Manager context menu.

Rated 5 out of 5 stars (36)
144,937 users

ChatZilla Requires Restart

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

Rated 4 out of 5 stars (126)
102,719 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 4 out of 5 stars (233)
98,840 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)
93,212 users

Send Later Requires Restart

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

Rated 5 out of 5 stars (80)
72,412 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 (311)
58,190 users

Copy Plain Text 2 Requires Restart

Copies text without formatting

Rated 5 out of 5 stars (81)
40,748 users

Mail Redirect Requires Restart

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

Rated 4 out of 5 stars (124)
39,044 users

Disable Add-on Compatibility Checks (Version 40+)

Reinstates the extensions.checkCompatibility preference.

Rated 5 out of 5 stars (3)
37,508 users

QuickNote Requires Restart

A simple note-taking extension.

Rated 5 out of 5 stars (166)
28,170 users

Diagnostics for Adblock Plus

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

Not yet rated
26,428 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 (53)
21,654 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 (56)
19,415 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 (45)
18,223 users

AutoCopy 2 Requires Restart

Copies selected text to the clipboard automatically.

Rated 5 out of 5 stars (63)
18,140 users

Copy As Plain Text Requires Restart

Removes formatting from copied text.

Rated 4 out of 5 stars (60)
16,260 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 (46)
13,711 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)
11,459 users