| seq | XtalView Xfit Sequence Data |
| seqbac | SEQ Backup Data |
| ser | Noptel NOS Statistics Series Data |
| server | Bonobo Activation API Data |
| serverdef | Eclipse WTP Server Definition Data |
| ses | SPECCTRA Session File |
| ses | Adobe Audition v2 Session |
| ses | Zemax Session Data |
| sess | PHP Session Data |
| sesx | Adobe Audition Session |
| set | PLINK END-terminated Variant Set Membership List |
| set | Raynen-Qili KnitCAD Pattern Expansion Data |
| set | Sibelius Sound Set Definition |
| settingcontent-ms | Microsoft Windows 10 Settings Data |
| sev | Sevilla Tournament Data |
| sevz | Sevilla Compressed Tournament Data |
| sew | Janome Stitch-based Embroidery Data |
| sew | Carlson 2016 Sewer Network Data |
| sez | SEEP/W ZIP Compressed Data |
| sf | RMCProfile Sulphur and Fluorine Data |
| sf | StatGraphics Centurion Data |
| sf0 | Windows Sytem File Check Data |
| sf1 | Census Bureau Summary File 1 |
| sf2 | SAS Consolidation Database |
| sf3 | StatGraphics Centurion Data |
| sf6 | StatGraphics Centurion Data |
| sf7 | SAS Consolidation Database |
| sfap0 | Sound Forge Audio Proxy |
| sfarr | SynthFont Arrangement Data |
| sfc | SNES ROM Image SMC |