| sln | Microsoft Visual Studio Solution |
| slp | Adobe RoboHelp Screen Layout Page |
| slz | Adobe RoboHelp Exported Screen Layout |
| smali | Android Smali Assembly Source Code |
| smap | JSP Source Map File |
| smcl | Stata SMCL Log |
| smpi | LINDO SMPI File |
| smps | LINDO SMPS File |
| smrc | Smtools Repository Data |
| smw | Crestron SIMPL Program |
| sni | MDK Archive |
| snippet | Visual Studio IntelliSense Code Snippet |
| 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 |