| .S2S | CED (Cambridge Electronics designs) | File di testo | Spike2 Script File | Spike2 | CED (Cambridge Electronics designs) |
| .S5D | Siemens AG | File di testo | Siemens Step 5 Source Code File | Step5 | Siemens AG |
| .SA6 | DeLorme | File di testo | Street Atlas Ver. 6 Map Document | DeLorme Street Atlas USA | DeLorme |
| .SAF | DeLorme | File di testo | Street Atlas USA Map File | DeLorme Street Atlas USA | DeLorme |
| .SAM | Microsoft Corporation | File di testo | LMHOSTS Sample File | Notepad++ | Don Ho |
| .SAVE | Unknown Developer | File di testo | Nano Temporary Save File | GNU nano | Open Source |
| .SCC | Microsoft Corporation | File di testo | SourceSafe Source Code Control File | Microsoft Visual Studio | Microsoft Corporation |
| .SCM | Gimpel Software | File di testo | GIMP Script-Fu Script | GIMP | The GIMP Development Team |
| .SCT | Scitex | File di testo | Scitex Continuous Tone File | Adobe Photoshop | Adobe Systems Incorporated |
| .SCW | Genie | File di testo | Score Writer Document | GenieSoft Score Writer | Genie |
| .SDM | Oracle Corporation | File di testo | StarOffice Mail Message | StarOffice | Oracle Corporation |
| .SDOC | Samsung Electronics | File di testo | Samsung Memo File | Samsung Kies | Samsung Electronics |
| .SDW | LizardTech | File di testo | MrSID World File | ESRI ArcGIS for Desktop | ESRI (Environmental Systems Research Institute) |
| .SE | Unknown Developer | File di testo | Shuttle Document | Microsoft Notepad | Microsoft Corporation |
| .SESSION | Dassault Systèmes | File di testo | CATIA 4 Session File | Adobe Acrobat DC | Adobe Systems Incorporated |
| .SFP | Troy | File di testo | Soft Font Printer File | TROY Printer Utility | Troy |
| .SGM | VBA Team | File di testo | VisualBoyAdvance Saved Game | VisualBoyAdvance | VBA Team |
| .SHF | Symantec Corporation | File di testo | Pretty Good Privacy (PGP) Share | Pretty Good Privacy (PGP) | Symantec Corporation |
| .SIG | Unknown Developer | File di testo | Signature File | Microsoft Outlook Express | Microsoft Corporation |
| .SL | SourceForge | File di testo | Unix Software License File | Vi | SourceForge |
| .SLA | Open Source | File di testo | Scribus Document | Scribus | Open Source |
| .SLF | Symantec Corporation | File di testo | Symantec License File | Symantec Ghost Solution Suite | Symantec Corporation |
| .SM | Open Source | File di testo | StepMania Song File | StepMania | Open Source |
| .SMF | Oracle Corporation | File di testo | StarMath Formula File | Apache OpenOffice | Apache Software Foundation |
| .SMH | Oracle Corporation | File di testo | Sealed MHT Document | Unsealer | Oracle Corporation |
| .SMS | Sega | File di testo | Sega Master System ROM | Kega Fusion | Steve Snake |
| .SOD | id Software | File di testo | Spear Of Destiny Data File | Spear of Destiny | id Software |
| .SPN | Corel | File di testo | Corel WordPerfect Distribution Definition | Corel WordPerfect | Corel |
| .SSA | Open Source | File di testo | Sub Station Alpha Subtitle File | VirtualDub | Open Source |
| .SSC | Microsoft Corporation | File di testo | SourceSafe Status File | Microsoft Visual Studio | Microsoft Corporation |
| .ST1 | Converge Horizons | File di testo | DigiTitle Master Subtitle File | DigiTitle Master | Converge Horizons |
| .STORY | Storyist Software | File di testo | Storyist Document | Storyist | Storyist Software |
| .STQ | StatSoft, Inc. | File di testo | Statistica Text File | STATISTICA | StatSoft, Inc. |
| .STRINGS | Apple | File di testo | Text Strings File | MacroMates TextMate | MacroMates |
| .STW | Oracle Corporation | File di testo | StarOffice Document Template | Apache OpenOffice | Apache Software Foundation |
| .STY | Jørgen Sørensen / Jososoft | File di testo | Yamaha/Korg Keyboard Style | Style Fixer | Jørgen Sørensen / Jososoft |
| .SUB | URUWORKS | File di testo | Subtitle File | CyberLink PowerDVD | CyberLink |
| .SUBTITLE | Pegasys | File di testo | TMPGEnc Subtitle File | TMPGEnc | Pegasys |
| .SWX | Apache Software Foundation | File di testo | OpenOffice.org 1.0 Text Document | Apache OpenOffice | Apache Software Foundation |
| .SXG | Oracle Corporation | File di testo | Apache OpenOffice Master Document | Apache OpenOffice | Apache Software Foundation |
| .SXW | Oracle Corporation | File di testo | StarOffice Writer Document | Apache OpenOffice | Apache Software Foundation |
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