| S | Source code file (Scheme) |
| S3I | Instrument file (Scream Tracker v 3.0) |
| S3M | 16 channel music file (Scream Tracker v 3.0) |
| SAI | Encrypted video file (Integrated Sensors) |
| SAL | Datafile (SORITEC) |
| SAM | Signed 8bit sample data file |
| SAR | Compressed archive (SAR) |
| SAS | SAS program file |
| SAS7BCAT | SAS system catalog |
| SAS7BDAT | SAS system data set |
| SAS7BNDX | SAS system index |
| SAV | Backup file (Generic) |
| SAVE | Doom 3 and Quake 4 Savegame File |
| SAVE | Temp file for Unix nano text editor |
| SB | Raw Signed Byte (8bit) audio data |
| SB! | Locking file (Superbase) |
| SBD | Data definition file (Superbase) |
| SBD - File Format | SAP 2000 file Structural Analysis Program from CSI.inc |
| SBF | File data (Superbase) |
| SBI | Instrument file (Creative Labs SoundBlaster) |
| SBK | Bank file (Soundblaster)/EMU SoundFont v1.x (Creative Labs Soundfont 1.0) |
| SBL | Flash object (ShockWave) |
| SBP | Program file (Superbase) |
| SBQ | Query definition file (Superbase) |
| SBR | Support file (Source Browser) |
| SBT | Notes related to record data (Superbase 4 for Windows) |
| SBV | Form definition file (Superbase) |
| SC | Display driver (Framework II) |
| SC2 | SAS 6.12 catalog (Windows 95/NT, OS/2, Mac) |
| SC3 | Renamed dBase III screen mask file (dBase IV) |
| SC4 | Level file (Roller Coaster Tycoon) |
| SC7 | SAS 8.2 catalog |
| SCA | Datafile (SCA) |
| SCC | Text file (Generic) |
| SCD | Object description language graphics (Scodl Scan Conversion) |
| SCF | Multimedia show (ScoreMaker) |
| SCH | Schematics file (ORCAD) |
| SCI | System configuration information file (Generic) |
| SCM | Video game console ROM emulater file |
| SCN | Screen file (Kermit) |
| SCN | Scene data file (TrueSpace2) |
| SCO | High score file (Generic game file) |
| SCP | Script file (BITCOM) |
| SCPT | Macintosh script-based file |
| SCR | Fax image (Generic) |
| SCREENFLOW | Screenflow screen recording application file |
| SCT | CT bitmap (Scitex) |
| SCT01 | SAS catalog (Unix) |
| SCTP | Applescript script |
| SCV | CASmate Native format (ScanVec) |
| SCX | Bitmap graphics (ColorRIX) |
| SCY | Security file (ReaGeniX) |
| SD | Audio (Sound Designer I) |
| SD2 | SAS 6.12 data set (Windows 95/NT OS/2, Mac) |
| SD7 | SAS 8.2 data set |
| SDA | File archive description (Fidonet Software Distribution Network) |
| SDC | Spreadsheet (Staroffice)(StarCalc) |
| SDD | Presentation file (Staroffice)(Starimpress) |
| SDF | System Data File Format - legacy Unisys (Sperry) format |
| SDI | Software distribution network information file |
| SDK | Floppy disk image (Roland) |
| SDL | Library file (SmartDraw) |
| SDN | Software distribution network compressed archive |
| SDP | Datafile (Cocreate SolidDesigner) |
| SDPC | Datafile (Cocreate SolidDesigner) |
| SDR | Drawing (SmartDraw) |
| SDS | Raw Midi Sample Dump Standard file |
| SDT | Template (SmartDraw) |
| SDV | Semicolon Divided Values file |
| SDW | Raw Signed DWord (32bit) data |
| SDW | Graphic file (Lotus WordPro) |
| SDX | Midi Sample Dump Standard files compacted by SDX |
| SEA | Self-expanding archive (used by Stuffit for Mac files and possibly by others) |
| SEC | Secured animation file (Disney Animation Studio) |
| SED | Screen editor script files (SED) |
| SEL | Data file (Copy Books) |
| SEP | Printer seperator page (Generic) |
| SEQ | Sequential instruction file (Bubble Chamber) |
| SES | Session information file (Clarion Modula-2) |
| SESSION | Internet Security Scanner file (ISS) |
| SET | Install driver sets (Symphony) |
| SET | Voice set files (Quartet) |
| SEW | Sewing program file (Generic) |
| SF | Wps attribute storage file (OS/2 WorkPlace Shell) |
| SF2 | Bank file (Creative Labs Soundfont 2.0)(Soundblaster) |
| SFD | Sound File Data (SoundStage) |
| SFI | Graphics file (SIS Framegrabber) |
| SFK | Sound file (Sonic Foundry) |
| SFL | Pcl 4 bitmap font (Ventura Publisher) |
| SFN | Font file (SPX) |
| SFP | Pcl bitmap font (Intellifont) |
| SFP | Pcl bitmap font (Portrait) |
| SFR | Sample Resource (Sonic Foundry) |
| SFS | Pcl 5 scalable font file (Intellifont) |
| SFT | SoftGrid Program Package Container |
| SFW | Mangled JPEG (Seattle Filmworks) |
| SFX | Self-extracting archive (RAR) |
| SG | Image file (SnapGraphix) |
| SG1 | Graphics file (Stanford Graphics) |
| SGF | Graphics file (Sonique) |
| SGI | Graphics file (Silicon Graphics) |
| SGML | Standard Generalized Markup Language |
| SGP | Statistics file (STATGRAPHICS Plus) |
| SGT | Save/Get keyboard macro (Signature) |
| SH | ASCii archive (Unix/SHAR) |
| SH3 | Presentaion file (Harvard Graphics) |
| SHB | Document shortcut file |
| SHG | Bitmap (HotSpot) |
| SHK | Compressed archive (Arthurian Shrink Archiver) |
| SHM | Shell macro (WordPerfect for Windows Library) |
| SHN | Audio compression file (Shorten) |
| SHP | File format used by some programs for 3D modeling of multipart interactive triangle models |
| SHP | DOS shapes file (3D Studios) |
| SHR | File archive (Unix ASCii) (SHAR) |
| SHS | Shell scrap file; reportedly used to send "password stealers" |
| SHT | Pocket Spreadsheets file |
| SHTML | HTML file containing Server Side Includes (SSI) |
| SHW | Presentation (Harvard Graphics 2.0) |
| SHX | Shapefile spatial index file (ArcView) |
| SIF | Setup installation files (Microsoft Windows NT) |
| SIG | Signature file (PopMail) |
| SIK | Backup files (Sicherungskopie) |
| SIT | Compressed archive of Mac files (Stuffit) |
| SIZ | Configuration file (Oracle 7) |
| SIZED | Gallery resized photo image |
| SKA | Secret Keyring file (PGP) |
| SKF | Drawing file (AutoSketch) |
| SKL | Resource file (Macromedia Director) |
| SL | Source code file (S-Lang) |
| SLB | Slide Library File (AutoCAD) |
| SLC | Compiled SALT script (Telix) |
| SLD | Slide File (AutoCAD) |
| SLDASM | SolidWorks Assembly File |
| SLDDRW | SolidWorks Drawing File |
| SLDPRT | SolidWorks Part File |
| SLI | Slide file (MAGICorp Slide Service) |
| SLK | Symbolic link spreadsheet (SLYK) |
| SLL | Sound data file (Generic) |
| SLT | Script application language (SALT) (Telix script source) |
| SM | Maillist (SoftSpoken Mailer) |
| SM | Simple MODRATEC Graphic |
| SM | Source code file (Smalltalk) |
| SM3 | Symbol file (DataCAD) |
| SMD | Video game console ROM emulator file |
| SMF | Fax document (SMARTFAX) |
| SMF | MIDI audio file |
| SMM | Macro (AMI Pro) |
| SMP | Samplevision format |
| SMS | Emulator ROM image file (8-bit Sega Master System) |
| SMT | SmartObject file (IconAuthor) |
| SMW | Simpl Windows for Crestron processors |
| SMZIP | Stepmania package format |
| SNA | Drive Snapshot compressed Disk Image file |
| SND | Sound resource (Macintosh) |
| SNDR | Sound file (Sounder) |
| SNDT | Sound file (SndTool) |
| SNG | Midi song file (Prism) |
| SNK | Visual Studio Strong-Name key file |
| SNM | Mailbox (mail folder) index (Netscape) |
| SNO | Source code file (Snobol4) |
| SNP | Output video file (Computer Eyes) |
| SO | Shared library file (Unix)(equivalent to a Windows DLL) |
| SOL | Solution file (Common used with game examples,tutorials) |
| SOM | Sort information files (Paradox) |
| SON | Song file (Creative Labs SoundBlaster Studio II) |
| SOU | Sound file (Creative Labs SoundBlaster Studio) |
| SP | Compressed archive for Unix (Sprint) |
| SP2 | Quake2 pcx 8-bit sprite builder file |
| SP3 | Quake2 pcx 32-bit sprite builder file (for use with CyberPunkQE) |
| SP4 | Saved game (Roller Coaster Tycoon) |
| SPA | FutureSplash Flash file (Macromedia) |
| SPC | Temporary file (WordPerfect for Windows) |
| SPD | Scalable font (Speedo) |
| SPF | JPEG image file |
| SPG | Glossary file (Sprint) |
| SPI | Graphics file (Phillips Scanner) |
| SPL | Sample file (DigiTracker) |
| SPM | Data file (WordPerfect for Windows) |
| SPP | Printer file (Sprint) |
| SPPACK | Sound sample (SP Pack) |
| SPR | Generated screen program (Microsoft FoxPro) |
| SPRITE | Bitmap file (Acorn) |
| SPS | Screen driver (Sprint) |
| SPT | Support file (MITAC disk/system management utility package) |
| SPU | Picture file (Spectrum 512) |
| SPW | Worksheet (SigmaPlot) |
| SPX | Compiled screen program (Microsoft FoxPro) |
| SPZ | SudoKoach puzzle file |
| SQC | Structured Query Language (SQL) common code file |
| SQL | Generally used by database products as an extension for SQL queries (scripts, text, or binary) |
| SQM | Windows Live Messenger log file |
| SQP | Query result of audio search (Sonique) |
| SQR | Structured Query Language (SQL) program file |
| SQZ | Compressed archive (SQUEEZE) |
| SRE | Undefined file (Motorola) |
| SRF | Raster graphics file (Sun) |
| SRM | Video game console ROM emulator file |
| SRP | SCript file (QuickLink) |
| SRZ | Source file (DataFlex) |
| SS | Bitmap graphics (Splash) |
| SS4 | MODRATEC SigScribe4 Railway Signal Interlocking Design Data File |
| SS5 | MODRATEC SigScribe5 Railway Signal Interlocking Design Data File |
| SSA | Video file (Sub Station Alpha) |
| SSD | Base SAS data file |
| SSD01 | SAS data sets (Unix) |
| SSF | Spreadsheet file (Enable) |
| SSP | Datafile (SAS Transport) |
| SSV | Quake 2 Savegame File |
| ST | Instrument library (Scream Tracker) |
| STA | Stack file (SpinMaker Plus) |
| STB | Stub library (Genus GX Kernel) |
| STD | State transition diagram graphic file (Prosa) |
| STE | Standardized graphic exchange file format |
| STEP | Standardized graphic exchange format |
| STF | Compressed archive (SHRINKTOFIT) |
| STG | Alphacet Strategy XML file |
| STL | Stereolithography file |
| STM | Music module (MOD) (Scream Tracker 2) |
| STO | Pascal stub OBJ file (Genus GX Kernel) |
| STP | Catia file |
| STQ | Text file (Statistica) (StatSoft Software) |
| STR | Structure list OBJ file (dBase IV Application Generator) |
| STS | Song file (Music) (Scream Tracker) |
| STT | Taci Pixia palette file |
| STW | OpenOffice.org 1.0 Text Document Template |
| STX | Tax form (CA-Simply Tax) |
| STY | Style sheet (Generic text and graphics programs |
| SUE | Lossless data compression and archival format from System Enhancement Associates (an alternative for ARC) |
| SUI | Suit library (Simple User Interface Toolkit) |
| SUM | Summary file (Generic) |
| SUN | Rasterfile graphics (Sun) |
| SUP | Supplementary dictionary files (WordPerfect for Windows) |
| SVD | Autosave file for document (WordPerfect for Windows) |
| SVF | Simple Vector Format 2D image (Microstation) |
| SVG | Scalable vector graphics file (Adobe) |
| SVP | Graphics file (Sonique) |
| SVS | Autosave file for style sheet (WordPerfect for Windows) |
| SVX | Interchange file format, 8SVX/16SV |
| SVY | Database file (SAVVY/PC) |
| SW | Raw signed Word (16bit) data |
| SWA | Shockwave audio file in Macromedia Director (an MP3 file) |
| SWF | Object (ShockWave Flash) |
| SWG | Swag Packet file (SWAG Reader) |
| SWITCH | Egress Software Technologies' container format for encrypted files |
| SWP | Document backup file (Sprint) |
| SXC | OpenOfficeCalc file |
| SXD | StarOffice Drawing |
| SXW | OpenOffice.org 1.0 Text Document |
| SY1 | Smartpix symbol library (Ami Pro) |
| SY3 | Symbol file (Harvard Graphics 2.0) |
| SYD | Backup of startup files (QEMM) |
| SYLK | Microsoft Excel spreadsheet file |
| SYM | Program symbol table (Generic to compilers) |
| SYN | Synonym file (Microsoft Word 5.0) |
| SYS | Datafile (SYGRAPH) |
| SYW | Graphics symbols (Harvard Graphics) |
