| Send Tab to Device | | - | | |
| Session Exporter | | - | | |
| Session Manager | | - | | |
| Session box - Tabs manager | | - | | |
| SettingSanity | | - | | |
| Settings Buttons | | - | | |
| Show Profile | | - | | |
| Show Quit Warning | | - | | |
| Simple Add-on Manager | | - | | |
| Simple Locale Switcher | | - | | |
| Simple Window Resizer | | - | | |
| Slim Add-on Manager | | - | | |
| Sort and Search Customization Dialogs | | - | | |
| Stacked Inspector | | - | | |
| Stay On Top | | - | | |
| Stay-Open Menu | | - | | |
| StayInOnlineMode | | - | | |
| Strict Pop-up Blocker | | - | | |
| Stylish Sync | | - | | |
| Switch Private Browsing | | - | | |
| Switch Window Mode | | - | | |
| Switch plugins.click_to_play | | - | | |
| Switchy | | - | | |
| Tahoe Data Manager | | - | | |
| Task Manager | | - | | |
| The Book of Mozilla，15：1 in Japanese | | - | | |
| Theme Font Size Changer | | - | | |
| Thunderbird Biff | | - | | |
| Tidy Browser Button | | - | | |
| Time Restart | | - | | |
| Time Restart Reloaded | | - | | |
| Toggle JS | | - | | |
| Toggle Mixed Active Content | | - | | |
| Toggle Mixed Display Content | | - | | |
| Toggle Private Browsing | | - | | |
| ToggleV6 | | - | | |
| Toolbar Autohide | | - | | |
| TrayHotKey | | - | | |
| Tweak Network | | - | | |
| UI Changes | | - | | |
| UI Eraser | | - | | |
| UI Text Overrider | | - | | |
| URL n Extension Block(UnE Block) | | - | | |
| UbiShell | | - | | |
| Ubiquity | | - | | |
| UnMHT | | - | | |
| Universal Print | | - | | |
| Untrusted Add-on Switcher | | - | | |
| Vacuum Places Improved | | - | | |
| Version Number in Add-ons Manager | | - | | |
