| 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 | ProWorx NXT Search Data |
| src | General Source Code File |
| srd | Sybase PowerBuilder DataWindow |
| sre | Windows CE Embedded Rom Image |
| srm | Sybase PowerBuilder Menu |
| srq | Sybase PowerBuilder Query Object |
| srs | Sybase PowerBuilder Structure |
| sru | Sybase PowerBuilder User Object |
| srw | Sybase PowerBuilder Window |
| srz | DataFlex Source Code |
| ss | Scheme Source Code |
| ss2 | SAS Stored Program |
| ss7 | SAS Stored Program |
| ssc | Esterel Sorted Circuit Code |
| ssc | Visual SourceSafe Status File |
| ssmssln | SQL Server Management Studio Solution |
| ssq | ODBC Script |
| ssx | VersaPro Smart Store Document |
| ssy | IBM Rational SDL Suite Diagram |
| storyboard | Xcode Interface Builder Storyboard |
| stp | Microsoft Sharepoint Site Template |
| stp | HTML Help Stop Words |
| strings | Mac OS X Strings Resource File |
| strl | Esterel Source Code |