| smd | Sega Genesis ROM |
| smf | SmartCAM Manufacture File |
| smf | Lowrance StructureMap File |
| smg | USoft System Message Data |
| smg | 3DVIA Composer Model |
| smggeom | SolidWorks Composer Assembly Geometry Data |
| smgsce | SolidWorks Composer Scenario Definitions Data |
| smgview | SolidWorks Composer View Definitions Data |
| smgxml | SolidWorks Composer Assembly Structure Data |
| smh | Crysfire Data |
| smi | SMILES Chemical Document |
| smiles | SMILES Chemical Document |
| smime | OpenSSL S/MIME Format Message |
| sml | Simile Model |
| smlic | SMS Servant License Data |
| smmx | SimpleMind Mind Map Data |
| smo | SmartMorph Animation |
| smol | Spartan Molecule Data |
| smp | BrainVoyager QX Surface-based Statistical Data |
| smpak | SuperMemo UX Data |
| smpkg | SmartMusic Package File |
| smpo | SpeedView Meta Object |
| smpx | SmartMusic Accompaniment File |
| sms | My Phone Explorer SMS |
| smt | Apollo HiPer-SIx Database Memo |
| smx | SysMetrix Skin |
| smx | STATISTICA Matrix File |
| sn | Elnec Programmer Serialization File |
| sn1 | Drive Snapshot Backup Data |
| sn2 | Drive Snapshot Backup Data |
| sn3 | Drive Snapshot Backup Data |
| sn3 | ChessDB Name Data |
| sn4 | Drive Snapshot Backup Data |
| sn4 | Scid Name Data |
| sn5 | Drive Snapshot Backup Data |
