open.file.extension

What file won't open?
Type it. .done

Plain instructions for the file in front of you. No universal viewers, no junkware, no padding before the answer.

Stuck the other way round? Show file extensions in Windows is the place to start.

Documents & data

14
css A stylesheet, not a document doc The old Word format eml A saved email epub Ebooks outside the store apps html A web page as a file ics Calendar invites json Readable text, once you know how md Markdown plain text odt OpenDocument text pages Apple Pages, outside a Mac pdf Rarely hard to open, often hard to edit vcf Contacts in a file xls Old Excel, still everywhere xlsx Excel, with or without Excel

Images & design

14
ai Illustrator files bmp The ancient bitmap cbr Comic book archives cr2 Canon RAW dds Game texture images eps Old vector print format heic iPhone photos on Windows jp2 JPEG 2000, no browser left jpg The everyday photo nef Nikon RAW png Screenshots and graphics psd Photoshop, without Photoshop svg Vector graphics tif Scans and print masters

Video & audio

8
flac Lossless audio m3u A playlist, not the music m4b Audiobooks mkv Works fine, until it doesn’t mp4 When the everyday video won’t play swf Flash, after Flash vob DVD video files webm Web video outside the browser

Archives & discs

6
7z Windows 11 opens most .7z files with no extra app bin Identify the type first dmg Mac disc images iso Mount it, no burning rar Windows 11 now extracts it zip No app needed at all

3D, CAD & maker

6
dst Embroidery machine files dwg AutoCAD drawings dxf CAD exchange, the older one obj 3D models step CAD exchange format stl 3D printing files

System & app files

8
aae iPhone photo edits apk Android apps as files bak A backup of something dat Another identify-first case dll You don’t really open it fomod Game mod installers qbo QuickBooks bank data tmp Leftover temporary data

Downloads

3
crdownload An unfinished download download Safari’s unfinished download torrent A pointer, not the download

Nothing here for that yet. Check the spelling, since extensions are short, like .dst, or browse every guide on the site.