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