| stppk | SDL Trados Synergy Project Package |
| stpx | SchemaType Compiled Schema |
| str | Altair FEKO Solution Vector Data |
| str | STATISTICA Report File |
| str | dBASE Structure Object |
| str | STELLA Runtime |
| str | DataPerfect Structural Information Data |
| str | Avantes Avasoft v8 Single Data |
| string | Zoom Player General Text Data |
| string | UltraEdit String Data |
| strn | HyperCard Stack Converter Data |
| sts | AdriPSX Save State |
| sts | Nimbus 7 SAMS Status Data |
| sts | MemMaker Status Information File |
| stt | Streets & Trips Map Template |
| stv | SofTV Author File |
| stx | EditPlus Syntax Data |
| stx | SAS XPORT Transport File |
| sty | Tecplot 360 Style Data |
| styk | Stykz Stick Figure |
| stykz | Stykz Animation File |
| styles | Steam Client GUI Resources Data |
| styx | ChordWizard Songtrix Style Data |
| su2 | I2P Software Update File |
| su3 | I2P Software Update File |
| sua | Tim Newport-Peace Special Use Airspace Format File |
| sub | WRAP SIMD Sub-monthly Time Step Simulation Data |
| sublime-build | Sublime Text Build Data |
| sublime-menu | Sublime Text Menu Data |
| sublime-snippet | Sublime Text Snippet Data |
