| Old Search Fixed | | - | | |
| OmniSidebar | | - | | |
| Omnibar | | - | | |
| Omnibar Lite | | - | | |
| Omnibar Plus | | - | | |
| OneTab | | - | | |
| OopsTab | | - | | |
| Open Amazon in a new pinned tab with toolbar button | | - | | |
| Open Clipboard Links | | - | | |
| Open In Current Tab | | - | | |
| Open Link Foreground | | - | | |
| Open Link In Current | | - | | |
| Open Link in New Tab | | - | | |
| Open Link in Sidebar | | - | | |
| Open Link in Silent Tab | | - | | |
| Open Links in Sidebar | | - | | |
| Open Page in Private Window | | - | | |
| Open Search Notification | | - | | |
| Open Tab Count | | - | | |
| Open Tabs Next To Current Plus | | - | | |
| Open Tabs Next to Current | | - | | |
| Open about：permissions | | - | | |
| Open in Parent Tab | | - | | |
| Open in Sidebar | | - | | |
| OpenAttribute | | - | | |
| OpenCurrentTab | | - | | |
| OpenTabs | | - | | |
| Openintabs-erase | | - | | |
| Order Tabs by Domain | | - | | |
| OreTab | | - | | |
| Organize Search Engines | | - | | |
| Organize Status Bar | | - | | |
| Other Window | | - | | |
| Overlay Scrollbars | | - | | |
| OverlayScrollbars | | - | | |
| Page Info Button | | - | | |
| Page Source | | - | | |
| Page Title Eraser | | - | | |
| Page Title in URL Bar | | - | | |
| Pano | | - | | |
| Panorama Tab Group Name | | - | | |
| Panorama View | | - | | |
| Paste Onto New Tab Button | | - | | |
| Paste Onto New Tab Button Revived | | - | | |
| Peers | | - | | |
| Permanent List-all-tabs Button | | - | | |
| Personal Menu | | - | | |
| Personal Titlebar | | - | | |
| Personas | | - | | |
| Personas Expression | | - | | |
