| snk | .NET Strong Name Key |
| snw | Sweave Document |
| so | Unix Shared Library |
| soy | Google Closure Template |
| sp2 | SAS Permanent Utility |
| sp45 | SuperCard Player File |
| sp7 | SAS Permanent Utility |
| sparql | SPARQL Script |
| spdslog | SAS Scalable Performance Data Server Log |
| spec | RPM Package Specification |
| spk | Novell Netware Server Source Package |
| spkg | Windows Phone Driver Package |
| splx | SPLX Package |
| spml | TeleFinder Page |
| spr | Visual FoxPro Form Program |
| sprite | BYOB Sprite |
| sprite | Scratch v1 Sprite |
| sprite2 | Scratch v2 Sprite |
| sprx | Signed PPU Relocatable Executable |
| spt | ESPL Programming File |
| spy | WinTECH Socket Spy Log |
| spz | Crestron SIMPL Compiled Program |
| sq | Sysquake SQ Application |
| sqc | SQR Common Code |
| sqljet | Eclipse JET SQL Template |
| sqml | Standard Query Markup Language Document |
| sqo | Squeak Object |
| sqr | SQR Script |
| sqt | Compiled SQR Script |
| src | General Source Code File |
| src | ProWorx NXT Search Data |
| srd | Sybase PowerBuilder DataWindow |
| sre | Windows CE Embedded Rom Image |
| srm | Sybase PowerBuilder Menu |
| srq | Sybase PowerBuilder Query Object |