| Extension | File Description |
| .SD0 | Uncommon Files |
| .SD1 | Uncommon Files |
| .SD2 | Audio Files |
| .SD2F | Audio Files |
| .SD3 | Uncommon Files |
| .SD4 | Uncommon Files |
| .SD4LF | Uncommon Files |
| .SD4PP | Uncommon Files |
| .SD5 | Uncommon Files |
| .SD6 | Uncommon Files |
| .SD7 | Uncommon Files |
| .SD8 | Uncommon Files |
| .SD9 | Uncommon Files |
| .SDA | Vector Image Files |
| .SDAC | Uncommon Files |
| .SDB | 3D Image Files |
| .SDC | Spreadsheet Files |
| .SDD | Data Files |
| .SDE | Uncommon Files |
| .SDEF | Developer Files |
| .SDF | GIS Files |
| .SDG | CAD Files |
| .SDH | Uncommon Files |
| .SDI | Disk Image Files |
| .SDJ | Uncommon Files |
| .SDK | Uncommon Files |
| .SDKD | Data Files |
| .SDKM | Data Files |
| .SDL | Uncommon Files |
| .SDM | GIS Files |
| .SDML | Uncommon Files |
| .SDN | Compressed Files |
| .SDO | Uncommon Files |
| .SDOC | Encoded Files |
| .SDOT | Uncommon Files |
| .SDP | Data Files |
| .SDPX | Uncommon Files |
| .SDQ | Uncommon Files |
| .SDQ?? | Uncommon Files |
| .SDR | Raster Image Files |
| .SDS | Data Files |
| .SDS?? | Uncommon Files |
| .SDT | Page Layout Files |
| .SDTHEME | Uncommon Files |
| .SDTS | Uncommon Files |
| .SDU | Uncommon Files |
| .SDV | Uncommon Files |
| .SDW | GIS Files |
| .SDX | Audio Files |
| .SDY | Uncommon Files |
| .SDZ | Uncommon Files |
| .SD_ | Uncommon Files |
| .SE | Uncommon Files |
| .SE0 | Uncommon Files |
| .SE1 | Uncommon Files |
| .SE2 | Uncommon Files |
| .SE3 | Uncommon Files |
| .SE4 | Uncommon Files |
| .SE5 | Uncommon Files |
| .SE6 | Uncommon Files |
| .SE7 | Uncommon Files |
| .SE8 | Uncommon Files |
| .SE9 | Uncommon Files |
| .SEA | Compressed Files |
| .SEARCH-MS | Misc Files |
| .SEARCHCONN | System Files |
| .SEARCHL | Uncommon Files |
| .SEB | Uncommon Files |
| .SEC | Misc Files |
| .SECSTORE | Uncommon Files |
| .SECURITY | Uncommon Files |
| .sed | Uncommon Files |
| .SEE | Uncommon Files |
| .SEED | Executable Files |
| .SEEK | Uncommon Files |
| Extension | File Description |
| .SEEM | Uncommon Files |
| .SEF | Encoded Files |
| .SEG | Audio Files |
| .SEGER | Uncommon Files |
| .SEGMENT0 | Uncommon Files |
| .SEGMENT1 | Uncommon Files |
| .SEGMENT2 | Uncommon Files |
| .SEGMENT3 | Uncommon Files |
| .SEGMENT4 | Uncommon Files |
| .SEGMENT5 | Uncommon Files |
| .SEH | Uncommon Files |
| .SEI | Uncommon Files |
| .SEJ | Uncommon Files |
| .SEK | Uncommon Files |
| .SEL | Data Files |
| .SELECT | Uncommon Files |
| .SEM | Uncommon Files |
| .SEMA | Uncommon Files |
| .SEMD | Database Files |
| .SEMF | Database Files |
| .SEML | Uncommon Files |
| .SEN | Data Files |
| .SENSU | Uncommon Files |
| .SENSUX | Uncommon Files |
| .SENT | Uncommon Files |
| .SEO | Data Files |
| .SEP | Raster Image Files |
| .SEPROJECT | Uncommon Files |
| .SEQ | Audio Files |
| .SEQU | Settings Files |
| .SEQUENCE | Uncommon Files |
| .SER | Data Files |
| .SERIAL | Uncommon Files |
| .SERVER | Uncommon Files |
| .SERVICE | Uncommon Files |
| .SERVICES | Uncommon Files |
| .SES | Audio Files |
| .SESSION | 3D Image Files |
| .SESTYLES | Uncommon Files |
| .SET | Settings Files |
| .SET1 | Uncommon Files |
| .SET2 | Uncommon Files |
| .SET3 | Uncommon Files |
| .SETCLOCK | Uncommon Files |
| .SETPAY | Data Files |
| .SETREG | Data Files |
| .SETUP | Uncommon Files |
| .SETVERS | Uncommon Files |
| .SEU | Uncommon Files |
| .SEV | Uncommon Files |
| .SEW | CAD Files |
| .SEX | Uncommon Files |
| .SEY | Uncommon Files |
| .SEZ | Uncommon Files |
| .SE_ | Uncommon Files |
| .SF | Misc Files |
| .SF0 | Uncommon Files |
| .SF1 | Uncommon Files |
| .SF2 | Audio Files |
| .SF3 | Uncommon Files |
| .SF4 | Uncommon Files |
| .SF5 | Uncommon Files |
| .SF6 | Uncommon Files |
| .SF7 | Uncommon Files |
| .SF8 | Uncommon Files |
| .SF9 | Uncommon Files |
| .SFA | Uncommon Files |
| .SFAP0 | Audio Files |
| .SFARK | Uncommon Files |
| .SFB | Game Files |
| .SFC | Game Files |
| .SFCACHE | System Files |
| .SFD | Font Files |
| .SFD-HDSTX | Data Files |
| .SFD?? | Uncommon Files |
