This page provides a list of those file extensions that start with .a. The information given below is a summary and further details can be found by clocking on the summary next to the file extension of interest.

.aUNIX static library file | ADA source code file.
.acACwin project file | GNU Autoconf configuration script | AC3D geometry file | Acceleration record file.
.accGEM desk accessories file.
.accdbMicrosoft Access 2007 database file.
.aceACE Archiver compression file.
.actAction diagram (FoxPro) | Action File (Animation Master).
.acvAdobe Photoshop compensation curve file.
.adeMicrosoft Access project extension.
.adfAmiga disk file.
.admAddict Dictionary file | Group Policy Administrative Template file.
.adpMicrosoft Access project file | Dynamic web page.
.adzCompressed Amiga disk file.
.afwBullion firmware file.
.agdAgile Advantage file | AgileGraph data file.
.aiPostScript viewer | Acrobat Illustrator vector graphics file | AIwin project file.
.aidMapXtreme generated file.
.aifAudio Interchange File.
.aifcCompressed audio file.
.aiffAudio Interchange file.
.airAdobe AIR installation package file | Automated Image Registration linear spatial transformation file.
.aldAxapta Label Data file.
.algESRI Mapper File | HDLmaker file.
.alsPart of the Delphi help file system.
.ammAdaptive Message Macro file.
.ampArbitrary Map file.
.amvAudio-Video media file.
.aniAnimated cursor file.
.apnApneaGraph data file | Wallpaper graphics file | REC Navigation application.
.appVoxPro file | GEM file.
.applicationClickOnce application manifest file.
.appref-msClickOnce application reference file.
.apsBinary file.
.arcCompressed file.
.arjCompressed file.
.asFlash ActionScript file.
.asaxASP.NET application file.
.ascASCII text file.
.ascxVisual Studio custom user control source file.
.asfMedia player audio-visual file.
.ashxASP.NET HTTP handler file.
.aslACTIVE Solutions database file | Adobe Photoshop style layer file | Miranda IM Smiley definition file.
.asmAssembler file | Solid Edge assembly file | Pro ENGINEER assembly file.
.asmxSP.NET web services source file.
.aspActive Server page.
.aspxASP.NET file.
.aspx.csVisual C# source file.
.aspx.vbVB.Net source file.
.atfAdobe Transfer Functions file | Axon Text File.
.attEmail attachment.
.atxTexture plug-in (Animation Master)
.aty3D Topicscape association type file.
.auµ-law sound file.
.auxAuxiliary target file | Erdas Hierarchical File | LaTeX auxiliary reference file | ChiWriter auxiliary dictionary.
.av2Avatar2 model file (Animation Master)
.avaAvatar model file (Animation Master)
.aviAudio video file.
.awkAWK script file.
.axdASP.NET internal HTTP handler file | Actrix technical 2000 file.
.axeAutoRoute map export file.
.axrARCHPR project status file.

For further information about the file extension please do click on the summary next to the file extension in the list above.

We would like this listing to be complete and comprehensive, but recognised that we may have missed one and that new file types are being used all the time. So if you know of a file type that we have missed that should be listed here then please let us know.