| sdpc | CoCreate SolidDesigner Data |
| sdtbx | XTRF Terminology Database |
| sdtheme | Nintendo Desktop Manager Theme Data |
| sdtid | RSA SecurID Software Token Import Data |
| sdts | Spatial Data Transfer Standard File |
| sdv | WDK Static Driver Verifier Rules |
| sdxf | Structured Data eXchange Format Data |
| sdxm | SDX Signed Data |
| sdxx | Autodesk AutoCAD Civil 3D Survey Database Extended Properties |
| sdy | Starmoney Database File |
| se1 | AD Summation iBlaze Database |
| sea | MAXQDA Saved Search |
| searchconnector-ms | Windows Search Connector Data |
| seawifs | SeaWiFS Data |
| sec | Concordance User Management Control Data |
| sec | PTC Creo Section Data |
| sec | Migration Wizard Secondary IFF File |
| seco | MSX Configurator Software Update |
| secstore | Adobe Acrobat Security Store File |
| sedr | URAP Supplemental Experiment Data Record |
| see | LISCAD Database |
| seek | Word List Expert Seek List Data |
| seg | Mail.dat Segment File |
| seg2 | SEG-2 Data File |
| segd | SEG-D Data File |
| segy | SEG Y Data File |
| sel | LinkOne Selection List |
| sel | SAM hmmscore Selection Data |
| sem3d | SEMulator3D Model Data |
| seman | Xtext Semantics Data |