| ssdf | Simple Structured Data Format File |
| ssdl | Sonicfire Pro Music |
| sse | StrataSearch Data File |
| ssfn | Steam Guard Data |
| ssg | Investor's Toolkit Data |
| ssi | SAP Business Objects Shared Security Information File |
| ssii | ProReveal Test Data File |
| ssj | STAR Splice Junction Data |
| sskd | On Schedule Schedule Data |
| ssleay | SSLeay Data |
| sslf | HLSW Shared Server List |
| ssm | AQUA Disulphide Distance Restraints Summary Data |
| ssm | BrainVoyager QX SSM Data |
| ssml | Speech Synthesis Markup Language Source Code |
| ssn | Railway Operation Simulator Session Data |
| sso_pt | Foxit Reader Data |
| ssr | FLEXIT Singleshot Survey Raw Data |
| sss | Stardock WindowsBlinds Substyles |
| sst | Microsoft Serialized Certificate Store |
| ssup | Sonicfire Pro Update |
| ssw | Sony-Ericsson Firmware |
| ssy | ScreenShare Compressed Data |
| ssz | Spider Player Skin |
| st0 | HSPICE Simulation Summary Data |
| st0 | SPICE Status Data |
| st2 | SAS Audit Data |
| st7 | SAS Audit Data |
| sta | Adobe Photoshop CS Color Statistics |
| sta | STATISTICA Spreadsheet File |
| staad | STAAD Model Data |
| stad | STAToolkit Data |
| stak | HyperCard Stack Data |
| stam | STAToolkit Metadata |
| stan | Stan Model File |
| startupinfo | E-Prime StartupInfo File |