| Photobucket Uploader | | - | | |
| PeekURL | | - | | |
| Paste2.org | | - | | |
| PageRank for Firefox | | - | | |
| PageRank | | - | | |
| PageQuery | | - | | |
| PageExpand | | - | | |
| Page for Hatena Bookmark | | - | | |
| PDFMyURL | | - | | |
| PDF Mage | | - | | |
| Optimy Search | | - | | |
| OptimizeGoogle | | - | | |
| OpenLink | | - | | |
| OpenCompare | | - | | |
| OpenComment | | - | | |
| Open in Wayback Machine | | - | | |
| Open in Google Docs Viewer | | - | | |
| Open PDF in Google Docs Viewer | | - | | |
| Open IT Online | | - | | |
| Open ISBN | | - | | |
| Open GMail in a new pinned tab toolbar button | | - | | |
| Online Convert | | - | | |
| Ondoku (Voice Reading) | | - | | |
| Old Google Image Search | | - | | |
| OffTheShelf | | - | | |
| Octotree | | - | | |
| Nyan Cat | | - | | |
| NoteTake | | - | | |
| No Cookie for Google search | | - | | |
| Niconico Downloader | | - | | |
| NicoFox | | - | | |
| Nice Translator | | - | | |
| Niccori Comment | | - | | |
| News-Topic-Blocker | | - | | |
| NewLiveWall! | | - | | |
| Netograph | | - | | |
| National Geographic Picture of the day | | - | | |
| NBA Scoreboard | | - | | |
| My Youtube | | - | | |
| My Map | | - | | |
| My Contributions (crash report edition) | | - | | |
| Multifox | | - | | |
| Multi engine search | | - | | |
| Multi Web Search | | - | | |
| MozTweak | | - | | |
| Moviesearcher | | - | | |
| Movie Critiques | | - | | |
| More Compact GMail | | - | | |
| Momiji Bookmark Button | | - | | |
| Mobile Wikipedia (WebExtension) | | - | | |