| .PAGES | Apple | File di testo | Apple Pages Document | LibreOffice | The Document Foundation |
| .PCO | Unknown Developer | File di testo | PC-Outline Outline | Unknown Software | Unknown Developer |
| .PCW | Bob Wallance | File di testo | PC Write Text Document | PC-Writer | Bob Wallance |
| .PDL | PDL Developerment Team | File di testo | Perl Data Language File | perldl | Open Source |
| .PDQ | Patton & Patton Software | File di testo | Flow Charting PDQ File | Flow Charting | Patton & Patton Software |
| .PDU | Unknown Developer | File di testo | Protocol Data Unit Message | Apple TextEdit | Apple |
| .PFX | Various Developers | File di testo | PKCS #12 Certificate File | Adobe Acrobat DC | Adobe Systems Incorporated |
| .PGW | Sublime HQ Pty Ltd | File di testo | Map World File | Sublime Text | Sublime HQ Pty Ltd |
| .PJT | Golden Software LLC | File di testo | Didger Project File | Golden Software Didger | Golden Software LLC |
| .PMO | Broderbund | File di testo | Print Meta Object File | Broderbund PrintMaster v7 Platinum | Broderbund |
| .PMP | Autodesk, Inc. | File di testo | AutoCAD Plot Model Parameter File | Autodesk AutoCAD | Autodesk, Inc. |
| .PMX | Yu Higuchi | File di testo | MikuMikuDance Model File | MikuMikuDance | Yu Higuchi |
| .PN2 | Tooraj Enayati | File di testo | ParsNegar II Document File | ParsNegar | Tooraj Enayati |
| .PNR | PEERNET Inc. | File di testo | PEERNET Label Designer File | Peernet Label Designer | PEERNET Inc. |
| .PPD | Adobe Systems Incorporated | File di testo | PostScript Printer Description File | Adobe PageMaker | Adobe Systems Incorporated |
| .PPG | Microsoft Corporation | File di testo | Microsoft PowerPoint Presentation | Microsoft PowerPoint | Microsoft Corporation |
| .PRN | Various Developers | File di testo | HP PCL Printer Output | Canvas X | ACD Systems |
| .PRT | PTC | File di testo | Pro/ENGINEER Part File | Autodesk Fusion 360 | Autodesk, Inc. |
| .PSW | Microsoft Corporation | File di testo | Windows Password Reset Disk File | Password Reset Disk | Microsoft Corporation |
| .PT | Open Source | File di testo | Zope Page Template | Zope | Open Source |
| .PT3 | Harvard Graphics | File di testo | Harvard Device Driver File | Harvard Graphics ChartXL | Harvard Graphics |
| .PT4 | Adobe Systems Incorporated | File di testo | Adobe PageMaker 4 Template | Adobe PageMaker | Adobe Systems Incorporated |
| .PT5 | Adobe Systems Incorporated | File di testo | PageMaker 5.0 Template File | Adobe PageMaker | Adobe Systems Incorporated |
| .PTL | IBM | File di testo | Rational Rose Petal File | IBM Rational Rose development software | IBM |
| .PUB | Microsoft Corporation | File di testo | Microsoft Publisher Document | LibreOffice | The Document Foundation |
| .PVM | Parallels | File di testo | Parallels Virtual Machine | VMware Fusion | VMware |
| .PWD | Microsoft Corporation | File di testo | Microsoft Pocket Word Document | Softmaker Office | SoftMaker Software |
| .PWI | Microsoft Corporation | File di testo | Pocket Word Document | Apache OpenOffice | Apache Software Foundation |
| .QPF | Act-3D | File di testo | Quest3D Project File | Quest3D | Act-3D |
| .RAD | Reality Pump Studios | File di testo | Reality Adlib Tracker Module | Adlib Tracker II | Adlib Tracker II |
| .RCJ | Microsoft Corporation | File di testo | Robocopy Job File | Microsoft Notepad | Microsoft Corporation |
| .RD | Sublime HQ Pty Ltd | File di testo | R Document File | Sublime Text | Sublime HQ Pty Ltd |
| .RDF | Unknown Developer | File di testo | Resource Description Framework File | Mozilla Firefox | Mozilla |
| .REA | Microsoft Corporation | File di testo | Readme Text File | Microsoft Notepad | Microsoft Corporation |
| .README | The Document Foundation | File di testo | Readme Text Document File | LibreOffice | The Document Foundation |
| .RFT | Autodesk, Inc. | File di testo | Revit Family Template File | AutoCAD Architecture | Autodesk, Inc. |
| .RIS | Research Systems, Inc | File di testo | Research Information Systems Citation File | EndNote | Thomson Reuters Corporation |
| .RP1 | RescuePro Production GbR | File di testo | RescuePro Physician Invoice File | RescuePro | RescuePro Production GbR |
| .RP5 | RescuePro Production GbR | File di testo | RescuePro Physician Invoice File | RescuePro | RescuePro Production GbR |
| .RPN | Swiftpage, Inc. | File di testo | ACT! Report Data | Act! | Swiftpage, Inc. |
| .RPT | SAP | File di testo | Crystal Reports File | Microsoft Visual Studio | Microsoft Corporation |
| .RPTDESIGN | Open Source | File di testo | BIRT Report Design | BIRT | Open Source |
| .RSP | Rockwell Automation Inc. | File di testo | RSLogix PLC Program File | RSLogix 5 | Rockwell Automation Inc. |
| .RST | David Goodger | File di testo | ReStructuredText File | Microsoft Notepad | Microsoft Corporation |
| .RTD | Autodesk, Inc. | File di testo | Robot Structural Analysis Design File | Robot Structural Analysis Professional | Autodesk, Inc. |
| .RTF | Microsoft Corporation | File di testo | Rich Text Format File | Corel WordPerfect X8 | Corel |
| .RTFD | Apple | File di testo | Rich Text Format Directory File | Apple TextEdit | Apple |
| .RTL | Hewlett-Packard | File di testo | Raster Transfer Language File | SwiftView | SwiftView, Inc. |
| .RTX | The Document Foundation | File di testo | Rich Text Document | LibreOffice | The Document Foundation |
| .RU | Microsoft Corporation | File di testo | Russian Text Or Localization File | Microsoft Notepad | Microsoft Corporation |
| .RUN | Open Source | File di testo | Linux Executable File | Linux | Open Source |
| .RVF | Interscape | File di testo | RichView Format File | TRichView | Interscape |
| .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 |
| .TAB | Microsoft Corporation | File di testo | Tab Separated Data File | Microsoft Excel | Microsoft Corporation |
| .TAL | Adobe Systems Incorporated | File di testo | Adobe TypeAlign Text Illustration File | Adobe TypeAlign | Adobe Systems Incorporated |
| .TBASIC | Eros Olmi | File di testo | ThinBasic Script | thinBasic | Eros Olmi |
| .TCM | IMSI/Design, LLC | File di testo | TurboCAD Mac Drawing | IMSI TurboCAD Deluxe | Redway3d and others |
| .TDF | DVD Copy | File di testo | Title Definition Format File | DVD X Copy | DVD Copy |
| .TDO | Xilinx, Inc. | File di testo | Xilinx Text Design Output Data | Xilinx CORE Generator System | Xilinx, Inc. |
| .TEM | E J Software | File di testo | Badge Designer 2000 Data | Badge Designer 2000 | E J Software |
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