| sdw | Visual SourceSafe SDW Data |
| sdx | Smart Diary Suite Temporary Data |
| 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 | Migration Wizard Secondary IFF File |
| sec | PGP Secret Keyring Data |
| sec | Pro/ENGINEER Sketch Data |
| sec | PTC Creo Section Data |
| 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 |
| seg | WaterGEMS Segmentation Analysis Results Data |
| seg2 | SEG-2 Data File |
| segd | SEG-D Data File |
| segy | SEG Y Data File |
| sel | Corel Paint Shop Pro Selection |
| sel | LinkOne Selection List |
| sel | SAM hmmscore Selection Data |
| sem3d | SEMulator3D Model Data |
| seman | Xtext Semantics Data |
