| Extension | File Description |
| .SHZ | Uncommon Files |
| .SI | 3D Image Files |
| .SI0 | Uncommon Files |
| .SI1 | Uncommon Files |
| .SI2 | Uncommon Files |
| .SI3 | Uncommon Files |
| .SI4 | Uncommon Files |
| .SI5 | Uncommon Files |
| .SI6 | Uncommon Files |
| .SI7 | Uncommon Files |
| .SI8 | Uncommon Files |
| .SI9 | Uncommon Files |
| .SIA | Uncommon Files |
| .SIAG | Uncommon Files |
| .SIB | Audio Files |
| .SIC | Uncommon Files |
| .SID | Raster Image Files |
| .SIDESPREAD | Uncommon Files |
| .SIE | Uncommon Files |
| .SIERRA | Uncommon Files |
| .SIF | Settings Files |
| .SIG | Text Files |
| .SIGN | Uncommon Files |
| .SIGNUP | Uncommon Files |
| .SIH | Uncommon Files |
| .SII | Uncommon Files |
| .SIJ | Uncommon Files |
| .SIK | Uncommon Files |
| .SIL | Uncommon Files |
| .SILK | Uncommon Files |
| .SILO | Data Files |
| .SIM | Raster Image Files |
| .SIMPLE | Uncommon Files |
| .SIMS2PACK | Game Files |
| .SIN | Uncommon Files |
| .SIO | Uncommon Files |
| .SIP | Uncommon Files |
| .SIQ | Uncommon Files |
| .SIQ?? | Uncommon Files |
| .SIR | Uncommon Files |
| .SIS | Backup Files |
| .SISHEN | Uncommon Files |
| .SISX | Misc Files |
| .SIT | Compressed Files |
| .SIT?? | Uncommon Files |
| .SITAR | Uncommon Files |
| .SITE | Web Files |
| .SITES | Uncommon Files |
| .SITHQX | Uncommon Files |
| .SITX | Compressed Files |
| .SIU | Uncommon Files |
| .SIV | Video Files |
| .SIW | Uncommon Files |
| .SIX | Uncommon Files |
| .SIXEL | Uncommon Files |
| .SIY | Uncommon Files |
| .SIZ | Uncommon Files |
| .SIZED | Uncommon Files |
| .SJ | Text Files |
| .SJ0 | Uncommon Files |
| .SJ1 | Uncommon Files |
| .SJ2 | Uncommon Files |
| .SJ3 | Uncommon Files |
| .SJ4 | Uncommon Files |
| .SJ5 | Uncommon Files |
| .SJ6 | Uncommon Files |
| .SJ7 | Uncommon Files |
| .SJ8 | Uncommon Files |
| .SJ9 | Uncommon Files |
| .SJA | Uncommon Files |
| .SJB | Uncommon Files |
| .SJC | Uncommon Files |
| .SJD | Uncommon Files |
| .SJE | Uncommon Files |
| .SJF | Uncommon Files |
| Extension | File Description |
| .SJG | Uncommon Files |
| .SJH | Uncommon Files |
| .SJI | Uncommon Files |
| .SJJ | Uncommon Files |
| .SJK | Uncommon Files |
| .SJL | Uncommon Files |
| .SJM | Uncommon Files |
| .SJN | Uncommon Files |
| .SJO | Uncommon Files |
| .SJP | Uncommon Files |
| .SJPG | Uncommon Files |
| .SJQ | Uncommon Files |
| .SJR | Uncommon Files |
| .SJS | Uncommon Files |
| .SJT | Uncommon Files |
| .SJU | Uncommon Files |
| .SJV | Uncommon Files |
| .SJW | Uncommon Files |
| .SJX | Uncommon Files |
| .SJY | Uncommon Files |
| .SJZ | Uncommon Files |
| .SJ_ | Uncommon Files |
| .SK | Misc Files |
| .SK0 | Uncommon Files |
| .SK1 | Uncommon Files |
| .SK2 | Uncommon Files |
| .SK3 | Uncommon Files |
| .SK4 | Uncommon Files |
| .SK5 | Uncommon Files |
| .SK6 | Uncommon Files |
| .SK7 | Uncommon Files |
| .SK8 | Uncommon Files |
| .SK9 | Uncommon Files |
| .SKA | Uncommon Files |
| .SKB | Backup Files |
| .SKC | Data Files |
| .SKCARD | Uncommon Files |
| .SKD | Uncommon Files |
| .SKE | Uncommon Files |
| .SKELETON | Uncommon Files |
| .SKF | CAD Files |
| .SKG | Uncommon Files |
| .SKH | Uncommon Files |
| .SKI | Settings Files |
| .SKIN | Settings Files |
| .SKJ | Uncommon Files |
| .SKK | Uncommon Files |
| .SKL | 3D Image Files |
| .SKM | Raster Image Files |
| .SKN | Settings Files |
| .SKNPRJ | Uncommon Files |
| .SKO | Uncommon Files |
| .SKP | 3D Image Files |
| .SKQ | Uncommon Files |
| .SKR | Misc Files |
| .SKS | Uncommon Files |
| .SKT | Uncommon Files |
| .SKU | Uncommon Files |
| .SKV | Data Files |
| .SKW | Uncommon Files |
| .SKWRITE | Uncommon Files |
| .SKX | Data Files |
| .SKY | Uncommon Files |
| .SKZ | Settings Files |
| .SK_ | Uncommon Files |
| .SL | Settings Files |
| .SL0 | Uncommon Files |
| .SL1 | Uncommon Files |
| .SL2 | Uncommon Files |
| .SL3 | Uncommon Files |
| .SL4 | Uncommon Files |
| .SL5 | Uncommon Files |
| .SL6 | Uncommon Files |
| .SL7 | Uncommon Files |
| .SL8 | Uncommon Files |
