| .AME | Sage | Datové soubory | ACT! E-mail System Library | Act! | Swiftpage, Inc. |
| .AMM | Bolide Software | Datové soubory | All My Movies Database File | Bolide All My Movies | Bolide Software |
| .AMN | Microsoft Corporation | Datové soubory | Aero Studio 2008 Menu Data | Aero Studio | Microsoft Corporation |
| .AMR | Open Source | Datové soubory | Adaptive Multi-Rate Codec File | Apple QuickTime Player | Apple |
| .AMSM | Atom Park | Datové soubory | Atomic Mail Sender Project | Atomic Mail Sender | Atom Park |
| .AMT | Planit Solutions, Inc. | Datové soubory | Alphacam 3D Mill, 2D Mill Tool | Planit Alphacam | Planit Solutions, Inc. |
| .AMU | Sony | Datové soubory | PictureGear Studio Photo Album File | PictureGear Studio | Sony |
| .AMW | Anark Corporation | Datové soubory | Anark Media Studio Workspace | Anark Studio | Anark Corporation |
| .AN1 | DeLorme | Datové soubory | Street Atlas USA Draw File | DeLorme Street Atlas USA | DeLorme |
| .AN8 | Steven Glanville | Datové soubory | Anim8or File | Anim8or | Steven Glanville |
| .ANA | Cuylaerts Engineering | Datové soubory | Analysis For Windows File | Analysis for Windows | Cuylaerts Engineering |
| .ANB | IBM | Datové soubory | Analytical Chart | i2 Analyst's Notebook | IBM |
| .ANDROID | Unknown Developer | Datové soubory | Android Readme File | Microsoft Notepad | Microsoft Corporation |
| .ANIME | Smith Micro Software | Datové soubory | Anime Studio Document | Smith Micro Moho Debut 12 | Smith Micro Software |
| .ANKI | Damien Elmes | Datové soubory | Anki Deck Data | Anki | Damien Elmes |
| .ANL | Planit Solutions, Inc. | Datové soubory | Alphacam Nest List | Planit Alphacam | Planit Solutions, Inc. |
| .ANN | ABBYY | Datové soubory | Lingvo Dictionary Annotation File | ABBYY Lingvo Dictionary | ABBYY |
| .ANS | Open Source | Datové soubory | ANSI Text File | Microsoft Notepad | Microsoft Corporation |
| .ANT | Open Source | Datové soubory | Radio Mobile Antenna Definition | Radio Mobile | Open Source |
| .ANYDVD | RedFox | Datové soubory | AnyDVD Registration Key | AnyDVD HD | RedFox |
| .AOI | Open Source | Datové soubory | Art Of Illusion 3D Scene | Art of Illusion | Open Source |
| .AOT | Novell, Inc. | Datové soubory | Novell Application Object Template | NetWare | Novell, Inc. |
| .APC | Savvius, Inc. | Datové soubory | AiroPeek Wireless Trace Capture File | AiroPeek | Savvius, Inc. |
| .APG | Unknown Developer | Datové soubory | Ivana Animated GIF File | Unknown Software | Unknown Developer |
| .APH | Ability Plus Software | Datové soubory | Ability Album File | Ability Office | Ability Plus Software |
| .APJ | The FreeBSD Community | Datové soubory | FreeBSD File | FreeBSD | The FreeBSD Community |
| .APP | Nokia | Datové soubory | Symbian OS Application | Symbian OS | Nokia |
| .APPLE | Apple | Datové soubory | Apple AppleSingle Data File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .APPS | Apple | Datové soubory | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .APX | Ability Plus Software | Datové soubory | Ability Photopaint Studio Image | Ability Office | Ability Plus Software |
| .AQ | Incline Software | Datové soubory | Ancestral Quest Genealogy Data | Ancestral Quest | Incline Software |
| .AQZ | Open Source | Datové soubory | Amateur Radio Questionary Data File | AQZ File Parser for Java | Open Source |
| .ARCH | Unknown Developer | Datové soubory | Illum Source Dotfiles File | Unknown Software | Unknown Developer |
| .ARH | Siemens AG | Datové soubory | ProTool Compressed Project File | Siemens ProTool | Siemens AG |
| .ARMOURFONT | Apple | Datové soubory | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .ARN | Microsoft Corporation | Datové soubory | Autoruns Data File | Microsoft Autoruns | Microsoft Corporation |
| .ARS | Adobe Systems Incorporated | Datové soubory | After Effects Render Settings File | Adobe After Effects | Adobe Systems Incorporated |
| .ART | Autodesk, Inc. | Datové soubory | ArtCAM Model | ArtCAM | Autodesk, Inc. |
| .ARV | Microsoft Corporation | Datové soubory | Microsoft Autoroute User Information File | Microsoft AutoRoute | Microsoft Corporation |
| .AS | Adobe Systems Incorporated | Datové soubory | Adobe ActionScript File | Microsoft Notepad | Microsoft Corporation |
| .AS4 | askSam Systems | Datové soubory | AskSam Backup File | askSam Systems SurfSaver | askSam Systems |
| .ASC | Symantec Corporation | Datové soubory | PGP (Pretty Good Privacy) ASCII Armored File | Mozilla Thunderbird | Mozilla |
| .ASHPRJ | Ashampoo | Datové soubory | Ashampoo Burning Studio Project | Ashampoo Burning Studio 18 | Ashampoo |
| .ASJ | Aldfaer Foundation | Datové soubory | Aldfaer Genealogy File | Aldfaer | Aldfaer Foundation |
| .ASM | Open Source | Datové soubory | Assembly Language Source Code File | Microsoft Notepad | Microsoft Corporation |
| .ASND | Adobe Systems Incorporated | Datové soubory | Adobe Sound Document | Adobe Audition | Adobe Systems Incorporated |
| .ASQ | Unit4 | Datové soubory | AGRESSO SQL Statement Data | AGRESSO SQL | Unit4 |
| .ASR | Adobe Systems Incorporated | Datové soubory | ActionScript Remote Document | Adobe Dreamweaver | Adobe Systems Incorporated |
| .AST | Apple | Datové soubory | ClarisWorks Assistant File | Apple AppleWorks | Apple |
| .AT2 | Adobe Systems Incorporated | Datové soubory | Adobe Persuasion Auto Template | Aldus PhotoStyler | Adobe Systems Incorporated |
| .ATD | Planit Solutions, Inc. | Datové soubory | Alphacam Lathe Drawing | Planit Alphacam | Planit Solutions, Inc. |
| .ATF | Molecular Devices | Datové soubory | Axon Text File | Microsoft Excel | Microsoft Corporation |
| .ATM | E-on Software, Inc. | Datové soubory | Vue Atmospheres File | E-on Vue | E-on Software, Inc. |
| .ATOMSVC | Microsoft Corporation | Datové soubory | Atom Service Document | Microsoft Excel | Microsoft Corporation |
| .ATS | DB Software Laboratory | Datové soubory | Advanced ETL Transformation Script | Advanced ETL Processor | DB Software Laboratory |
| .ATTR | Apple | Datové soubory | iPhoto Attributes File | Apple iPhoto | Apple |
| .ATW | Unknown Developer | Datové soubory | Attityd Survey Program Data | Unknown Software | Unknown Developer |
| .AUC | Jordysoft | Datové soubory | AUC Database | Advanced URL Catalog | Jordysoft |
| .AUD | Interscape | Datové soubory | Video Game Compressed Audio File | Command and Conquer | Interscape |
| .AUDIO | Apple | Datové soubory | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .AUS | SourceForge | Datové soubory | AutoREALM Symbols | AutoREALM | SourceForge |
| .AVA | Open Source | Datové soubory | AvaaBook eBook | AvaaPlayer | Open Source |
| .AVC | Kaspersky Lab | Datové soubory | Kaspersky Virus Database File | Kaspersky Anti-Virus | Kaspersky Lab |
| .AVG | AVG Technologies | Datové soubory | AVG Antivirus Virus Database | AVG Antivirus | AVG Technologies |
| .AVH | Pioneer DJ Corporation | Datové soubory | Pioneer AVH Firmware Update | Pioneer AVH | Pioneer DJ Corporation |
| .AVL | ESRI | Datové soubory | ArcView Legend File | ESRI ArcGIS for Desktop | ESRI (Environmental Systems Research Institute) |
| .AVP | Avid Technology | Datové soubory | Avid Project File | Avid Media Composer | Avid Technology |
| .AVS | Adobe Systems Incorporated | Datové soubory | Adobe Photoshop Variations File | Adobe Photoshop | Adobe Systems Incorporated |
| .AW | Microsoft Corporation | Datové soubory | Answer Wizard File | Microsoft Excel | Microsoft Corporation |
| .AWF | Adobe Systems Incorporated | Datové soubory | Adobe WorkFlow Workgroup Plugin | Adobe Creative Cloud | Adobe Systems Incorporated |
| .AWR | Lavasoft | Datové soubory | Ad-Aware Reference File | Ad-Aware | Lavasoft |
| .AWX | ESRI | Datové soubory | ArcIMS XML Project File | ArcIMS | ESRI |
| .AX2 | Apex Software | Datové soubory | Ver. 2 Sketch File | Apex | Apex Software |
| .AXL | Wattle Software | Datové soubory | XML File | MacroMates TextMate | MacroMates |
| .AXP | Canneverbe Limited | Datové soubory | CDBurnerXP Audio Compilation File | Canneverbe CDBurnerXP | Canneverbe Limited |
| .AXS | Microsoft Corporation | Datové soubory | ActiveX Script File | Microsoft Notepad | Microsoft Corporation |
| .AZK | Jonathan Forster | Datové soubory | DMDX Output Document | DMDX | Jonathan Forster |
| .AZW3F | Amazon | Datové soubory | Amazon eBook Metadata File | Amazon Kindle | Amazon |
| .AZZ | Antanas Zdramys | Datové soubory | AZZ Cardfile Database File | AZZ Cardfile | Antanas Zdramys |
| .AZZX | Antanas Zdramys | Datové soubory | Uncompressed AZZ Cardfile Data File | AZZ Cardfile | Antanas Zdramys |
| .A_T | Unknown Developer | Datové soubory | Atrain File | Unknown Software | Unknown Developer |
z 2 
