En filtype er tre eller fire karakterer for enden af filnavnet, så som .docx, .PDF eller .txt. Filtyperne fortæller dig, hvilken type fil, det er, og hvilket program, der kan åbne den. Disse filtyper anvendes i driftssystemerne Microsoft Windows, Mac OS X og Linux.

De mest kendte filtyper

tekstfiler

.docx	Microsoft Open Word XML Document
.doc	Microsoft Word Document
.txt	Plain Text File
.rtf	Revit Family Template File
.odt	OpenOffice/StarOffice File

lydfiler

.mp3	MP3 Audio File
.wav	Wave Audio File
.aac	MPEG-2 Advanced Audio Coding File
.wma	Windows Media Audio File
.m4a	MPEG-4 Audio File

videofiler

.avi	Audio Video Interleave File
.mp4	MPEG-4 Video File
.mov	Video Clip
.flv	Video File
.mpg	MPEG 1 System Stream

datafiler

.pdf	Portable Document Format File
.xls	Excel Spreadsheet File
.csv	Comma Separated Values File
.ini	Initialization/Configuration File
.html	Hypertext Markup Language File

komprimeringsarkiver

.zip	ZIP File
.rar	WinRAR Compressed Archive
.7z	Compressed File
.tar	Consolidated Unix File Archive
.gz	GNU Zipped Archive File

eksekverbare filer

.exe	Windows Executable File
.msi	Windows Installer File
.bin	Binary Disc Image
.app	Punch Post
.dmg	Disk Copy Disk Image File