| .OFL | Ots Labs | Innstillingsfiler | OtsTurntables Playlist | OtsTurntables | Ots Labs |
| .OIF | OriginLab | Innstillingsfiler | Origin Import Filter File | OriginLan Origin Viewer | OriginLab |
| .OMS | Hewlett-Packard | Innstillingsfiler | HP Printer Substrate Presets Package File | HP Embedded Web Server | Hewlett-Packard |
| .ONETOC | Microsoft Corporation | Innstillingsfiler | Microsoft OneNote Table Of Contents | Microsoft OneNote | Microsoft Corporation |
| .ONETOC2 | Microsoft Corporation | Innstillingsfiler | Microsoft OneNote Table Of Contents File | Microsoft OneNote | Microsoft Corporation |
| .OODGUISETTINGS | O&O Software | Innstillingsfiler | O&O Defrag GUI Settings | O&O Defrag | O&O Software |
| .OPS | Microsoft Corporation | Innstillingsfiler | Office Profile Settings File | Microsoft Office | Microsoft Corporation |
| .OPT | LexisNexis | Innstillingsfiler | Concordance Database File | LexisNexis Concordance | LexisNexis |
| .OSDX | Microsoft Corporation | Innstillingsfiler | Search Connector Description File | Microsoft Windows | Microsoft Corporation |
| .OSS | Microsoft Corporation | Innstillingsfiler | Microsoft Outlook Saved Search File | Microsoft Outlook | Microsoft Corporation |
| .OTH | Apache Software Foundation | Innstillingsfiler | OpenDocument HTML Template | Apache OpenOffice | Apache Software Foundation |
| .OTZ | OpenLP Team | Innstillingsfiler | OpenLP Theme File | OpenLP | OpenLP Team |
| .OVPN | OpenVPN Technologies | Innstillingsfiler | OpenVPN Configuration File | OpenVPN | OpenVPN Technologies |
| .OXO | Open Source | Innstillingsfiler | Ox Object-oriented Matrix Programming Language Source Code | OX Professional | Open Source |
| .P2M | Dassault Systèmes | Innstillingsfiler | PhotoWorks Appearance File | SFW PhotoWorks | Seattle Lab |
| .P3E | Adobe Systems Incorporated | Innstillingsfiler | Photoshop Repousse Settings File | Adobe Photoshop CC | Adobe Systems Incorporated |
| .P7E | Electric Quilt | Innstillingsfiler | EQStitch 7 Project | Electric Quilt | Electric Quilt |
| .PAL | Corel | Innstillingsfiler | Painter Custom Palettes File | Corel Painter | Corel |
| .PAN | ProVUE Development | Innstillingsfiler | Panorama Database File | ProVUE Development Panorama | ProVUE Development |
| .PB | Fantaisie Software | Innstillingsfiler | PureBasic Source File | PureBasic | Fantaisie Software |
| .PB2 | Orinda Software Ltd | Innstillingsfiler | OrindaBuild Configuration File | OrindaBuild | Orinda Software Ltd |
| .PBP | Sony | Innstillingsfiler | PSP Firmware Update File | PBP Unpacker | Unknown Developer |
| .PBS | Corel | Innstillingsfiler | PaintShop Pro Brush Strokes | PaintShop Pro | Corel |
| .PBV | Corel | Innstillingsfiler | Paint Shop Pro Bevel Preset | PaintShop Pro | Corel |
| .PBZ | Google | Innstillingsfiler | Google Picasa Button ZIP Archive | Google Picasa | Google |
| .PC2 | Autodesk, Inc. | Innstillingsfiler | AutoCAD Plotter Configuration File | Autodesk AutoCAD | Autodesk, Inc. |
| .PC3 | Autodesk, Inc. | Innstillingsfiler | AutoCAD Plotter Configuration File | Autodesk AutoCAD | Autodesk, Inc. |
| .PCN | Corel | Innstillingsfiler | Corel Paint Shop Pro Contour Preset | PaintShop Pro | Corel |
| .PCP | Microsoft Corporation | Innstillingsfiler | Windows Installer Patch Creation Properties File | Microsoft Windows SDK | Microsoft Corporation |
| .PDF | Adobe Systems Incorporated | Innstillingsfiler | Portable Document Format File | LibreOffice | The Document Foundation |
| .PDP | Palo Alto Software | Innstillingsfiler | Palo Alto Software Plan Component File | Business Plan Pro | Palo Alto Software |
| .PEN | Corel | Innstillingsfiler | Paint Shop Pro Pen Preset File | PaintShop Pro | Corel |
| .PERFMONCFG | Microsoft Corporation | Innstillingsfiler | Performance Monitor Configuration File | Windows Performance Monitor | Microsoft Corporation |
| .PFK | Jeffrey C. Johnson | Innstillingsfiler | XTree Programmable Function Keys | XTree | Jeffrey C. Johnson |
| .PFS | Antonio Da Cruz | Innstillingsfiler | PhotoFiltre Studio Saved Selection File | PhotoFiltre | Antonio Da Cruz |
| .PGP | Autodesk, Inc. | Innstillingsfiler | AutoCAD Program Parameters File | Microsoft Notepad | Microsoft Corporation |
| .PH | Larry Wall | Innstillingsfiler | Perl Header File | Perl | Larry Wall |
| .PHB | Motorola | Innstillingsfiler | Motorola Phone Book File | Motorola Phone Tools | Avanquest Software |
| .PHL | Amazon | Innstillingsfiler | Kindle Popular Highlights File | Microsoft Notepad | Microsoft Corporation |
| .PIE | Carl Kenner | Innstillingsfiler | GlovePIE Controller Script | GlovePIE | Softonic Corporate |
| .PIO | Avid Technology | Innstillingsfiler | Pro Tools I/O Settings File | Avid Pro Tools | Avid Technology |
| .PIP | Microsoft Corporation | Innstillingsfiler | Office Personalized Settings File | Microsoft Excel | Microsoft Corporation |
| .PIW | PixAround | Innstillingsfiler | PI ProcessBook Display Definition File | PixMaker | PixAround |
| .PKG | Apple | Innstillingsfiler | Apple MacOS Installer Package | macOS | Apple |
| .PKGDEF | Microsoft Corporation | Innstillingsfiler | Microsoft Visual Studio Shell Data | Microsoft Visual Studio | Microsoft Corporation |
| .PL | Larry Wall | Innstillingsfiler | Perl Source Code | Microsoft Notepad | Microsoft Corporation |
| .PLB | Microsoft Corporation | Innstillingsfiler | Microsoft Robotics Developer Studio Playback Data | Microsoft Robotics Developer Studio | Microsoft Corporation |
| .PLG | Microsoft Corporation | Innstillingsfiler | Visual Studio Build Log File | Microsoft Visual Studio | Microsoft Corporation |
| .PLIST | Apple | Innstillingsfiler | Property List XML File | Microsoft Notepad | Microsoft Corporation |
| .PLS | Various Developers | Innstillingsfiler | Audio Playlist | VLC Media Player | VideoLAN |
| .PM5 | Adobe Systems Incorporated | Innstillingsfiler | PageMaker 5.0 Document | Adobe PageMaker | Adobe Systems Incorporated |
| .PM6 | Adobe Systems Incorporated | Innstillingsfiler | PageMaker 6.0 Document | Adobe InDesign | Adobe Systems Incorporated |
| .PMC | David Harris | Innstillingsfiler | Pegasus Mail Filter Rule Files | Pegasus Mail | David Harris |
| .PMJ | David Harris | Innstillingsfiler | Pegasus Mail Configuration File | Pegasus Mail | David Harris |
| .PMK | David Harris | Innstillingsfiler | Pegasus Mail Keyboard Settings | Pegasus Mail | David Harris |
| .PML | Microsoft Corporation | Innstillingsfiler | Process Monitor Log File | Process Monitor | Microsoft Corporation |
| .PMP | Autodesk, Inc. | Innstillingsfiler | AutoCAD Plot Model Parameter File | Autodesk AutoCAD | Autodesk, Inc. |
| .PNP | David Harris | Innstillingsfiler | Pegasus Mail POP3 Filter Rules | Pegasus Mail | David Harris |
| .POLICY | Oracle Corporation | Innstillingsfiler | Java Policy Implementation File | Java Virtual Machine | Sun Microsystems |
| .POW | Microsoft Corporation | Innstillingsfiler | Microsoft Windows Power Schema | Microsoft Windows | Microsoft Corporation |
| .PPG | Microsoft Corporation | Innstillingsfiler | Microsoft PowerPoint Presentation | Microsoft PowerPoint | Microsoft Corporation |
| .PPP | Serif | Innstillingsfiler | Serif PagePlus Document | PagePlus | Serif |
| .PPW | Corel | Innstillingsfiler | Micrografx Picture Publisher Wizard File | Micrografx Picture Publisher | Corel |
| .PQ | Eric Fredricksen | Innstillingsfiler | Progress Quest Save File | Progress Quest | Eric Fredricksen |
| .PQZ | Mystic Fractal | Innstillingsfiler | QuaSZ Palette Data | QuaSZ | Mystic Fractal |
| .PR | Source Dynamics, Inc. | Innstillingsfiler | Source Insight Project | Source Insight | Source Dynamics, Inc. |
| .PR3 | Adobe Systems Incorporated | Innstillingsfiler | Adobe Persuasion V3 Presentation | Adobe Persuasion | Adobe Systems Incorporated |
| .PRA | SofTech, Inc. | Innstillingsfiler | CADRA Design Drafting Software Data | CADRA | SofTech, Inc. |
| .PRB | John C. Miller | Innstillingsfiler | XyAlgebra Probabilities File | xyAlgebra | John C. Miller |
| .PREF | Unknown Developer | Innstillingsfiler | Preferences File | macOS | Apple |
| .PRF | Microsoft Corporation | Innstillingsfiler | Outlook Profile File | Microsoft Outlook 2016 | Microsoft Corporation |
| .PRM | Unknown Developer | Innstillingsfiler | Parameter File | GSAS | National Institute of Standards and Technology (NIST) |
| .PROFILE | GNU Operating System | Innstillingsfiler | Bash Shell Profile | MacroMates TextMate | MacroMates |
| .PROPERTIES | Mojang | Innstillingsfiler | Minecraft Properties File | Microsoft Notepad | Microsoft Corporation |
| .PROPS | Microsoft Corporation | Innstillingsfiler | Microsoft Visual Studio Property Sheet | Microsoft Visual Studio | Microsoft Corporation |
| .PROVXML | Microsoft Corporation | Innstillingsfiler | Microsoft Windows Provisioning XML Data | Windows Mobile | Microsoft Corporation |
| .PRP | IBM | Innstillingsfiler | Rational Model Properties File | IBM Rational Rose development software | IBM |
| .PRS | Software Publishing Corporation (SPC) | Innstillingsfiler | Harvard Graphics Presentation | Corel Presentations X8 | Corel |
| .PRT | PTC | Innstillingsfiler | Pro/ENGINEER Part File | Autodesk Fusion 360 | Autodesk, Inc. |
| .PRX | Microsoft Corporation | Innstillingsfiler | FoxPro Compiled Program | Microsoft Visual FoxPro | Microsoft Corporation |
| .PS1XML | Microsoft Corporation | Innstillingsfiler | Windows PowerShell Display Configuration File | Microsoft Windows PowerShell | Microsoft Corporation |
| .PSC1 | Microsoft Corporation | Innstillingsfiler | Windows PowerShell Console File | Microsoft Windows PowerShell | Microsoft Corporation |
| .PSC2 | Microsoft Corporation | Innstillingsfiler | Windows PowerShell Console File | Microsoft Windows PowerShell | Microsoft Corporation |
| .PSF | Adobe Systems Incorporated | Innstillingsfiler | Photoshop Proof Settings File | Adobe Photoshop Elements | Adobe Systems Incorporated |
| .PSP | Corel Corporation | Innstillingsfiler | PaintShop Pro Image | Corel Painter | Corel |
| .PSPROJ | Broderbund | Innstillingsfiler | The Print Shop Project File | The Print Shop | Broderbund |
| .PSY | Open Source | Innstillingsfiler | Psycle Song File | Psycle | Open Source |
| .PTF | Sony | Innstillingsfiler | PSP Theme File | PSP Theme Toolbox | Unknown Developer |
| .PTG | Pearson | Innstillingsfiler | PowerTeacher Gradebook Configuration File | PowerTeacher Gradebook | Pearson |
| .PTP | Avid Technology | Innstillingsfiler | Pro Tools Preferences File | Avid Pro Tools | Avid Technology |
| .PVS | Parallels | Innstillingsfiler | Parallels Desktop Configuration File | VMware vCenter Converter | VMware |
| .PVX | Kitware, Inc. | Innstillingsfiler | ParaView XML Configuration File | ParaView | Open Source |
| .PWS | Corel | Innstillingsfiler | Painter Workspace File | Corel Painter | Corel |
| .PWT | Autodesk, Inc. | Innstillingsfiler | AutoCAD Publish To Web Template | Autodesk AutoCAD | Autodesk, Inc. |
| .PXB | The Pixelmator Team | Innstillingsfiler | Pixelmator Brush File | Pixelmator | The Pixelmator Team |
| .PXG | The Pixelmator Team | Innstillingsfiler | Pixelmator Gradient File | Pixelmator | The Pixelmator Team |
| .PXS | The Pixelmator Team | Innstillingsfiler | Pixelmator Shape File | Pixelmator | The Pixelmator Team |
| .PZP | Application Techniques Inc. | Innstillingsfiler | Pizazz Plus Palette Settings File | Pizazz | Application Techniques Inc. |
| .PZS | Sonic Solutions | Innstillingsfiler | PhotoSuite Slide Show File | Roxio Creator NXT Pro 6 | Roxio |
| .Q1 | Nullsoft | Innstillingsfiler | Winamp Equalizer Preset File | Nullsoft Winamp | Nullsoft |
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