| News-Topic-Blocker | | - | | |
| Niccori Comment | | - | | |
| Nice Translator | | - | | |
| NicoFox | | - | | |
| Niconico Downloader | | - | | |
| No Cookie for Google search | | - | | |
| NoteTake | | - | | |
| Nyan Cat | | - | | |
| Octotree | | - | | |
| OffTheShelf | | - | | |
| Old Google Image Search | | - | | |
| Ondoku (Voice Reading) | | - | | |
| Online Convert | | - | | |
| Open GMail in a new pinned tab toolbar button | | - | | |
| Open ISBN | | - | | |
| Open IT Online | | - | | |
| Open PDF in Google Docs Viewer | | - | | |
| Open in Google Docs Viewer | | - | | |
| Open in Wayback Machine | | - | | |
| OpenComment | | - | | |
| OpenCompare | | - | | |
| OpenLink | | - | | |
| OptimizeGoogle | | - | | |
| Optimy Search | | - | | |
| PDF Mage | | - | | |
| PDFMyURL | | - | | |
| Page for Hatena Bookmark | | - | | |
| PageExpand | | - | | |
| PageQuery | | - | | |
| PageRank | | - | | |
| PageRank for Firefox | | - | | |
| Paste2.org | | - | | |
| PeekURL | | - | | |
| Photobucket Uploader | | - | | |
| Photozou Uploader | | - | | |
| PiP Video | | - | | |
| PicRange Rightclick Extension | | - | | |
| PicStorage.eu | | - | | |
| Picmasa Uploader | | - | | |
| PictuTools | | - | | |
| Picture Zoom Plus(+) | | - | | |
| PictureFox | | - | | |
| Pixlr | | - | | |
| Play／Pause | | - | | |
| PlugIn-Checker | | - | | |
| Popup Play | | - | | |
| Popup Video(WebExtension) | | - | | |
| Powerbot for Gmail | | - | | |
| Prefsearch | | - | | |
| Preview Peek for Google | | - | | |
