| stp | Microsoft Sharepoint Site Template |
| strings | Mac OS X Strings Resource File |
| strl | Esterel Source Code |
| sts | Squeak Source Code |
| stub | Mac OS X Stub Library |
| styl | Stylus CSS Script |
| su2 | SAS Utility |
| su7 | SAS Utility |
| sum | Stata Checksum File |
| summ | Clapack Blas Testing Data |
| suo | Visual Studio Solution User Options |
| sv | SystemVerilog File |
| svc | Microsoft IIS Special Content File |
| svcinfo | Visual Studio WCF Service Information File |
| svclog | WCF Service Trace Viewer Log |
| svcmap | Visual Studio WCF Service Map File |
| svd | CMSIS System View Description Data |
| svdl | Security Validation Description Language Document |
| svh | SystemVerilog Include File |
| svn | Subversion Data File |
| svn-base | Subversion Base Data |
| svn-work | Subversion Cache |
| svntmp | Subversion Temporary Data |
| swc | Shockwave Flash Component File |
| swd | Shockwave Flash Debug |
| swift | Swift Source Code |
| swt | Shockwave Flash Template |
| sxp | OpenOffice.org Script |
| syp | SYP Script |
| sysml | Systems Modeling Language Document |
| systag | Android System Tag Data |
| syt | Sytes Template File |
| t | Tom Source Code |
| t | Turing Source Code |
| t2p | Tex2Page Macro Code |