| File extension | The full name of the file |
|---|---|
| File extension O | Object Format |
| File extension O01 | Typhoon Voice |
| File extension O2C | Objects To See 3D |
| File extension O8D | OCTGN Deck |
| File extension O8G | OCTGN Game Definition |
| File extension O8O | Mediator 5 Repository Tabs Vorlagen.006 |
| File extension O8S | OCTGN Set |
| File extension OAB | Microsoft Outlook Offline Address Book Format |
| File extension OAD | Suite Notaro Document |
| File extension OAF | Microsoft Flight Simulator Texture |
| File extension OAM | Adobe Edge Overlay Format |
| File extension OAP | Samsung Bada Signed Installation Package |
| File extension OAR | OpenSimulator Archive Format |
| File extension OAS | Microsoft Outlook Attachment Sniffer |
| File extension OAT | Google Android RunTime Code |
| File extension OAV | Microsoft Flight Simulator Texture |
| File extension OAW | OpenArchitectureWare Workflow |
| File extension OAZ | NetFax Manager OAZ Fax Image |
| File extension OB | IBM LinkWay Object |
| File extension OB! | Orbit Downloader Incomplete Download Format |
| File extension OB3 | ABF Software Outlook Backup Backup |
| File extension OB5 | TopLang OE Backup |
| File extension OBAK | WinSQL Offline Backup |
| File extension OBB | Google Android Opaque Binary Blob Format |
| File extension OBD | Microsoft Office Binder Document Format |
| File extension OBF | OsmAnd Offline GPS Vector Maps |
| File extension OBG | ZBrush Mesh |
| File extension OBI | Microsoft Outlook 2007/2010/2013 RSS Subscription Format |
| File extension OBJ | 3D Object Format |
| File extension OBJX | Metatools Object Bryce Support |
| File extension OBK | OrCAD Capture Design Or Library |
| File extension OBL | TrueSpace |
| File extension OBML | Opera Mini Saved Web Page Format |
| File extension OBML15 | Opera Mini 5.1 Saved Web Page |
| File extension OBP | Bryce Object Format |
| File extension OBPACK | ObjectBar Theme Pack |
| File extension OBR | Borland C++ Object Browser Data |
| File extension OBS | WAsP Obstacle List |
| File extension OBT | Openbox Theme Format |
| File extension OBV | 3D Photo Browser Thumbnail Cache |
| File extension OBW | Toontrack Superior Drummer Audio Format |
| File extension OBX | Rational XDE |
| File extension OBYX | Obyx Control |
| File extension OBZ | Compressed 3D Object Format |
| File extension OC3 | OpenCanvas 3 Event Format |
| File extension OC4 | OpenCanvas 4 Event Format |
| File extension OC5 | OpenCanvas 5 Event Format |
| File extension OC9 | OrgCon Organization |
| File extension OCA | Custom Control Library Type Format |
| File extension OCAMLMAKEFILE | Caml Programming Language Makefile |
| File extension OCB | Origin Precompiled Origin C |
| File extension OCC | Oceanic DataPool Format |
| File extension OCD | OCAD Digitized Map Format |
| File extension OCDC | Mathematica Document |
| File extension OCDF | OneClickDigital Mp3 Audio Book |
| File extension OCE | Open Catalog Extension Connection Format |
| File extension OCEN | EdGCM Data |
| File extension OCF | OM2 Cipher |
| File extension OCG | Osprey Custom Graph |
| File extension OCI | OpenCanvas Image Format |
| File extension OCM | Netscape Communicator Aim |
| File extension OCP | Advanced Art Studio Image |
| File extension OCR | FaxGrapper FAX Transcribed Text Format |
| File extension OCT | RADIANCE Octree Format |
| File extension OCTEST | Xcode Objective-C Unit Test Bundle |
| File extension OCV | OCV Training Data |
| File extension OCX | ActiveX Control Format |
| File extension OC_ | Compressed ActiveX Control |
| File extension OD | Mascotte Mascopt Request Format |
| File extension OD1 | Omnis 5 Database |
| File extension OD2 | Omnis 5 Database |
| File extension OD3 | Omnis Studio Database |
| File extension OD4-9 | Omnis5 Database |
| File extension ODB | ArcView Object Database ASCII Format |
| File extension ODC | OpenOffice.org OpenDocument Format |
| File extension ODCCUBEFILE | OpenDocument 1 |
| File extension ODCNEWFILE | Microsoft Office Data Connection |
| File extension ODCTABLEFILE | Microsoft Office |
| File extension ODE | Microsoft Office |
| File extension ODEX | Google Android Optimized Executalbe |
| File extension ODF | Open Document Interchange Format (ODIF) |
| File extension ODG | OpenDocument Drawing Format |
| File extension ODH | Microsoft Visual Studio Interface Definition Language |
| File extension ODI | OpenOffice.org Image Format |
| File extension ODIF | Open Document Interchange Format |
| File extension ODL | Object Description Language Format |
| File extension ODM | OpenOffice.org OpenDocument Global Text Document Format |
| File extension ODO | ICUBE Online Operating System Write Document Format |
| File extension ODP | OpenOffice.org OpenDocument Presentation Format |
| File extension ODS | OpenDocument Spreadsheet Format |
| File extension ODT | ODF Text Document Format |
| File extension ODT# | OpenOffice.org Locked Document |
| File extension ODTPC | Oracle User Productivity Kit Presentation |
| File extension ODTTF | Microsoft Office Document Embedded Font |
| File extension ODV | Ocean Data View Data |
| File extension ODVI | LaTeX |
| File extension ODX | Microsoft BizTalk Server Diagram Format |
| File extension OD_ | Oracle Compressed Driver |
| File extension OEACCAOUNT | Windows Mail |
| File extension OEACCOUNT | Windows Mail Account Settings Format |
| File extension OEB | Open EBook Format |
| File extension OECL | Open EDA Component Library |
| File extension OEF | Optim Export |
| File extension OEM | OEM Install Data Format |
| File extension OEMIGACCOUNT | Outlook Express Temporary |
| File extension OET | ESignal Order Entry Ticket |
| File extension OEX | Opera Add-on Format |
| File extension OFA | Kodak OfotoNow |
| File extension OFB | Oxygen Forensic Suite Backup |
| File extension OFC | Open Financial Connectivity Format |
| File extension OFD | ObjectView Form Definition |
| File extension OFF | DEC 3D Object File Format |
| File extension OFFICEUI | Microsoft Office UI Customization |
| File extension OFFSETS | Offset |
| File extension OFL | OtsTurntables Playlist |
| File extension OFM | Adobe PostScript Font Description Format |
| File extension OFN | MS Office File New (Other Office Documents) |
| File extension OFP | Objecteering Project |
| File extension OFR | OptimFROG Encoded Audio |
| File extension OFS | OptimFROG Dualstream |
| File extension OFT | Microsoft Outlook Template Format |
| File extension OFX | Open Financial Exchange Format |
| File extension OGA | Ogg Vorbis Audio Profile Format |
| File extension OGD | Oracle Forms Graph |
| File extension OGF | S.T.A.L.K.E.R. Model Format |
| File extension OGG | Ogg Vorbis Audio Format |
| File extension OGL | ATI Overlay Source Code |
| File extension OGM | Ogg Vorbis Media Format |
| File extension OGNC | Dynamic Web Page Format |
| File extension OGO | Origin Graphic Object |
| File extension OGR | OGR C++ Open Source Library |
| File extension OGS | Origin Script Format |
| File extension OGV | Ogg Vorbis Video Format |
| File extension OGW | OriginLab Worksheet |
| File extension OGX | Ogg Vorbis Multiplex Profile |
| File extension OGZ | Cube 2 Sauerbraten Map Format |
| File extension OH | DrillAssistant List |
| File extension OH4 | Overhoor List |
| File extension OHP | MS-DOS 7 |
| File extension OHS | Bink Outbound History |
| File extension OHW | Overhoor DrillAssistant List |
| File extension OIF | QuickBase Web-sharable Database Interchange |
| File extension OIL | Open Image Library Format Image Format |
| File extension OJP | 3WayPack |
| File extension OK | Qedit |
| File extension OKM | OkMap Map Defining |
| File extension OKOZO | Okozo Desktop Animation |
| File extension OKR | PowerRecover One Key Recovery |
| File extension OKS | OKScript |
| File extension OKT | Oktalyzer Music Module (MOD) Format |
| File extension OKX | OKScript |
| File extension OL | Valve Hammer Object Layout |
| File extension OLA | Online Access Format |
| File extension OLB | Microsoft Office OLE Object Library Format |
| File extension OLB2 | CanOpener Library |
| File extension OLD | Backup Plus Backup Format |
| File extension OLE | Microsoft Object Linking And Embedding |
| File extension OLE2 | Microsoft Office Binary Document Container Format |
| File extension OLF | OyezForms Legal Documents |
| File extension OLK | Microsoft Outlook Address Book Format |
| File extension OLK14CATEGORY | Microsoft Outlook 2011 For Mac Category Format |
| File extension OLK14CONTACT | Microsoft Outlook 2011 For Mac Contact Format |
| File extension OLK14DBHEADER | Microsoft Outlook 2011 For Mac Database |
| File extension OLK14EVENT | Outlook Calendar Event Format |
| File extension OLK14FOLDER | Microsoft Outlook 2011 For Mac Folder |
| File extension OLK14GROUP | Outlook Group Format |
| File extension OLK14MAILACCOUNT | Microsoft Outlook 2011 For Mac Mail Account Settings Format |
| File extension OLK14MESSAGE | Microsoft Outlook 2011 For Mac Message Format |
| File extension OLK14MSGATTACH | Microsoft Outlook 2011 For Mac Message Attachment |
| File extension OLK14MSGSOURCE | Microsoft Outlook 2011 For Mac Message Source Format |
| File extension OLK14NOTE | Outlook Note Format |
| File extension OLK14PREF | Microsoft Outlook 2011 For Mac Preferences Format |
| File extension OLK14RECENT | Microsoft Outlook 2011 For Mac Recent Address |
| File extension OLK14RULE | Microsoft Outlook 2011 For Mac Rule |
| File extension OLK14SCHEDULE | Microsoft Outlook 2011 For Mac Schedule |
| File extension OLK14SEARCH | Microsoft Outlook 2011 For Mac Saved Search |
| File extension OLK14SIGNATURE | Microsoft Outlook 2011 For Mac Signature Format |
| File extension OLK14TASK | Outlook Task Format |
| File extension OLK14UID | Microsoft Outlook 2011 For Mac UID |
| File extension OLL | TrialDirector Load |
| File extension OLM | Microsoft Outlook For Mac Data Format |
| File extension OLN | Microsoft Visual C++ Outline Examples |
| File extension OLPROJ | Adobe OnLocation |
| File extension OLS | Microsoft Office List Shortcut |
| File extension OLT | Orbit Downloader Download List Format |
| File extension OLV | Roller Coaster Tycoon |
| File extension OLY | AFP Advanced Function Presentation Overlay Resource |
| File extension OMA | Sony OpenMG Music Format |
| File extension OMC | Origin Customized Menu |
| File extension OMCS | Office Manager Access Format |
| File extension OMD | MapInfo Routing J Server Data |
| File extension OMEG | Mathematica For Mac |
| File extension OMF | Open Media Framework Format |
| File extension OMFI | Open Media Framework |
| File extension OMG | O&O DiskImage Backup Format |
| File extension OML | TracePro Model |
| File extension OMN | Omnipotent Collection |
| File extension OMO | OMake Object Format |
| File extension OMOD | Oblivion Mod Manager Mod Format |
| File extension OMP | Office Manager Pro Document Archive |
| File extension OMR | OMR Template |
| File extension OMS | Order Maven |
| File extension OMT | SITH HLA Object Model Template |
| File extension OMX | OtsAV Media Library Information Format |
| File extension ON2 | On2 Encoded FLV |
| File extension OND | Lotus Notes Format |
| File extension ONE | Microsoft OneNote Document Format |
| File extension ONECACHE | Microsoft OneNote Cache |
| File extension ONEPKG | Microsoft OneNote Package Format |
| File extension ONETMP | Microsoft OneNote Temporary |
| File extension ONETOC | Microsoft OneNote Table Of Contents |
| File extension ONETOC2 | Microsoft OneNote Table Of Contents Format |
| File extension ONM | Outdoor Navigator Map |
| File extension ONT | TheWord Module Format |
| File extension ONTX | TheWord Encrypted Module Format |
| File extension ONW | Omron HMI NTST |
| File extension ONX | OnyxGrass Image |
| File extension OO3 | Omni Group Outliner 3 Format |
| File extension OOG | PyGraph Python Graphics Interface Object Oriented Graphics |
| File extension OOGL | Geomview Object Oriented Graphics Library |
| File extension OOK | Arachne Batch Script Format |
| File extension OOS | OpenOffice.org Spreadsheet |
| File extension OOT | OpenOffice.org Text |
| File extension OP | ESignal OptionsPlus |
| File extension OP2 | Outpost 2 Saved Game |
| File extension OP4 | Nastran Output |
| File extension OPA | Fly! RAW Image Opacity Map |
| File extension OPAL | Microsoft Office Customization Tool (OCT) Language-specific Settings |
| File extension OPAX | Microsoft Office Customization Tool (OCT) Standard Settings |
| File extension OPB | Bryce Object |
| File extension OPC | Microsoft Office 97 Upgrade Control |
| File extension OPD | Durango Interferometry Software Document Format |
| File extension OPDOWNLOAD | Opera Next Incomplete Download |
| File extension OPEF | OmniPass Encrypted Folder |
| File extension OPENBSD | OpenBSD Readme Format |
| File extension OPF | Open Packaging Format |
| File extension OPG | Offline Plan Generation Package |
| File extension OPI | Adlib OCR Processing Information |
| File extension OPJ | OrCAD Capture Project Format |
| File extension OPK | Sinking Island/LIle Noyée Game |
| File extension OPLC | Nokia Logo Format |
| File extension OPLM | Outline Processor Markup Language |
| File extension OPML | OPML Outline Processor Markup Language File Format |
| File extension OPN | Court Opinion |
| File extension OPP | IPhotoDVD |
| File extension OPPC | Space Marine Game Resource Package |
| File extension OPQ | Eschalon: Book I Game |
| File extension OPR | OPRO X Browser |
| File extension OPS | Microsoft Office Profile Settings Format |
| File extension OPT | MySQL Database Data Format |
| File extension OPTIONS | SE-SOFT Configuration Format |
| File extension OPTS | Linux Configuration Options Format |
| File extension OPUS | Opus Audio Format |
| File extension OPW | OrgPlus For Windows Organization Chart |
| File extension OPX | Microsoft Office Organization Chart File Format |
| File extension OPXT | OrpPlus Template |
| File extension OPY | OptiY Model |
| File extension OP_ | GKSetup Support |
| File extension OQY | Microsoft Excel OLAP Query Format |
| File extension OR2 | Lotus Organizer 2 Format |
| File extension OR3 | IBM Lotus Organizer 97 Format |
| File extension OR4 | Lotus Organizer Data Format |
| File extension OR5 | IBM Lotus Organizer Format |
| File extension OR6 | Lotus Organizer Data Format |
| File extension OR8 | Rational Rose Oracle8 Database Model Report |
| File extension ORA | Oracle Database Parameter Configuration Format |
| File extension ORB | Original EBook Reader Ebook |
| File extension ORC | CSound Orchestra Midi Format |
| File extension ORDEREDTEST | Microsoft Visual Studio Ordered Test Format |
| File extension ORE | Ore Executable Format |
| File extension ORF | Olympus Digital Camera Raw Image Format |
| File extension ORG | Lotus Organiser Format |
| File extension ORG2+ | Lotus Organizer |
| File extension ORI | Original Format |
| File extension ORIG | Original Format |
| File extension ORIGINAL | Netobjects Fusion Components Bbscomp Message |
| File extension ORIGINAL_EPUB | EPUB Ebook Backup |
| File extension ORIGINAL_MOBI | MOBI Ebook Backup |
| File extension ORK | Warhammer Mark Of Chaos Game Archive |
| File extension ORL | Object-Relational Language |
| File extension ORMDESIGNER | ORM Designer Project |
| File extension ORS | DSP Group TrueSpeech Audio Format |
| File extension ORT | COREX Orthographic Transcriptions Format |
| File extension ORV | Oracom Video Format |
| File extension ORX | RadiantOne Virtual Directory Server Database Schema |
| File extension ORZ | Holic Game |
| File extension OS | ObjectScript Source Format |
| File extension OS2 | Os2 System |
| File extension OS3 | OS/2 Warp 3 |
| File extension OSA | W32/Sober-AD |
| File extension OSAS | Apple Script Library Tani Script |
| File extension OSAX | FindFile OSAX Mac Format Type |
| File extension OSB | OpenStreetMap Binary Map Format |
| File extension OSBX | OneSafe Exported Backup |
| File extension OSC | Remote Installation Services Client Installation Wizard Format |
| File extension OSCD | TouchOSC Interface Editor Template |
| File extension OSD | Open Software Description |
| File extension OSDX | Microsoft Windows Search Connector Format |
| File extension OSF | Descent 3 Sound |
| File extension OSG | OSGJS JSON Input |
| File extension OSK | Osu! Skin Format |
| File extension OSL | OckamSoft Log |
| File extension OSM | OpenStreetMap Data Format |
| File extension OSP | OpenShot Project Format |
| File extension OSR | Osu! Game Replay Format |
| File extension OSS | Microsoft Office Saved Search Format |
| File extension OST | Microsoft Outlook Inbox Off-line Folder Format |
| File extension OSU | Osu! Dialog Format |
| File extension OSW | ONESWING Contents |
| File extension OSX | Apple Mac OS PowerPC Executable Format |
| File extension OSZ | Osu! Beatmap Format |
| File extension OT | TheWord Text Module Format |
| File extension OTA | OTA Bitmap Format |
| File extension OTB | Nokia OTA Bitmap Format |
| File extension OTC | OpenDocument Chart Template Format |
| File extension OTD | OpenIV Texture Data |
| File extension OTF | OpenType Font File Format |
| File extension OTG | OpenOffice.org Graphics Document Template |
| File extension OTH | OpenOffice.org OpenDocument HTML Text Template |
| File extension OTI | OpenDocument Image Template Format |
| File extension OTL | Super NoteTab Template Format |
| File extension OTLN | Opal Outline Format |
| File extension OTM | Microsoft Outlook Macro Format |
| File extension OTP | OpenOffice.org Presentation Template Format |
| File extension OTR | IRIX Complied FTR |
| File extension OTRKEY | OTRKEY Encoded Video Format |
| File extension OTS | OpenOffice.org OpenDocument Spreadsheet Template Format |
| File extension OTT | OpenOffice.org Text Document Template Format |
| File extension OTV | Rotor-Disc OTV Kit OTV Calibration |
| File extension OTX | TheWord Encrypted Module Format |
| File extension OTZ | OpenLP Theme Format |
| File extension OUT | Output Format |
| File extension OUTLINE | FontTwister Letter Outline |
| File extension OUTLOOK97 | Microsoft Outlook Custom Mail |
| File extension OUX | Bibexcel |
| File extension OV | OpenInsight Database Overflow |
| File extension OV1 | Overlay |
| File extension OV2 | TomTom Navigator Point Of Interest Format |
| File extension OV3 | Overlay |
| File extension OV4 | Overlay |
| File extension OV5 | Overlay |
| File extension OVA | Open Virtual Machine Format |
| File extension OVD | ObjectVision Data |
| File extension OVE | Overture Music Score Format |
| File extension OVF | Open Virtualization Format Package |
| File extension OVG | ObjectVision Converted Graphic |
| File extension OVH | OMSI Bus Settings |
| File extension OVL | Overlay Format |
| File extension OVOLOG | OoVoo Log |
| File extension OVP | The Overlay Maker Package Format |
| File extension OVPN | OpenVPN Config Format |
| File extension OVR | Overlay Format |
| File extension OVS | Ovation 1 Style Sheet |
| File extension OVW | Logic Pro Overview Format |
| File extension OW | Free Pascal For Windows Object Format |
| File extension OWC | OutWit Hub OutWit Catch Db Format |
| File extension OWG | OutWit Hub OutWit Gear Outwit Thesaurus Db Format |
| File extension OWL | OWL (Obfuscated Weird Language) Source Code Format |
| File extension OWM | OutWit Hub OutWit Mashup XML Format |
| File extension OWR | PeopleSoft Results Archive |
| File extension OWS | Web Studio Project |
| File extension OWT | Ancestry.com OneWorldTree |
| File extension OX | Ox Object-Oriented Matrix Programming Language |
| File extension OXD | PS3 Proxy Server |
| File extension OXF | IBM Rational Rhapsody |
| File extension OXO | Ox Object-Oriented Matrix Programming Language |
| File extension OXPS | Windows 8 OpenXPS Document Format |
| File extension OXT | OpenOffice.org Extension Help Format |
| File extension OXYGENE | Oxygene Project Format |
| File extension OYX | IBM Lotus Approach Alternate Database Index Format |
| File extension OYZ | Lotus Approach Alternate DBASE Index |
| File extension OZ | Opera Job Management Compressed Format |
| File extension OZF2 | OziExplorer Map |
| File extension OZFX3 | OziExplorer Image |
| File extension OZJ | Mu Online Graphic |
| File extension OZP | Orgadata LogiKal |
| File extension OZT | Mu Online Texture |
File extensions in alphabetical order: O
The list of file extensions, sorted alphabetically, beginning with the letter O