| nj | Nunjucks Template |
| njk | Nunjucks Template |
| njs | Nunjucks Template |
| nk | NUKE Script |
| nmf | Native Client Manifest File |
| nmk | NMake Makefile |
| nod | NetObjects Fusion Site File |
| nokogiri | Nokogiri Source Code |
| npmignore | NPM Ignore |
| nqc | Not Quite C Source Code |
| nse | Nmap Scripting Engine Script |
| nsh | NSIS Header |
| nsi | NSIS Script File |
| nsis | NSIS Script File |
| nuke | NUKE Script |
| nunj | Nunjucks Template |
| nunjs | Nunjucks Template |
| nunjucks | Nunjucks Template |
| nupkg | NuGet Package |
| nuspec | NuGet Specification Data |
| nut | Squirrel Source Code |
| nvb | NVSG SDK Scene Graph |
| nvv | Nvidia Vertex Shader Profile |
| nw | Sweave Document |
| nxb | C4 Engine Binary Model Data |
| nxc | Not eXactly C Source Code |
| nxd | AdaOS Debugging Information |
| nxg | eSite Builder NXG Web Page |
| nxu | C4 Engine XML Model Data |
| o | Compiled Object File |
| oat | Android Compiled OAT |
| ob2 | Oberon 2 Source Code |
| obak | WinSQL Offline Backup Data |
| obe | Objeck Executable File |
| obh | Hitachi Ladder Editor Object Program |