Windows file names have two parts separated by a period: first, the file name, and second, a three- or four-character extension that defines the file type. In expenses.xlsx, for example, the first part of the file name is expenses and the extension is xlsx.

Extensions tell your computer which application created or can open the file and which icon to use for the file. For example, the docx extension tells your computer that Microsoft Word can open the file and to display a Word icon when you view it in File Explorer.

Most file name extensions are compatible with more than one program that you have installed. You can change a file name extension, but that won't convert the file to another format or change anything else about it except the file name. To learn more about how to change which program will open a file, read Change default programs in Windows 10.

If you don’t see file name extensions when you view files in File Explorer:

  1. In the search box on the taskbar, type file explorer, and in the search results, select File Explorer.

  2. In File Explorer under View, in the Show/hide group, select the File name extensions check box.How to enable viewing file name extensions in Windows

Below is a list of common Windows file name extensions and formats.

Extension

Format

aac, adt, adts

Windows audio file

accdb

Microsoft Access database file

accde

Microsoft Access execute-only file

accdr

Microsoft Access runtime database

accdt

Microsoft Access database template

aif, aifc, aiff

Audio Interchange File format file

aspx

ASP.NET Active Server page

avi

Audio Video Interleave movie or sound file

bat

PC batch file

bin

Binary compressed file

bmp

Bitmap file

cab

Windows Cabinet file

cda

CD Audio Track

csv

Comma-separated values file

dif

Spreadsheet data interchange format file

dll

Dynamic Link Library file

doc

Microsoft Word document before Word 2007

docm

Microsoft Word macro-enabled document

docx

Microsoft Word document

dot

Microsoft Word template before Word 2007

dotx

Microsoft Word template

eml

Email file created by Outlook Express, Windows Live Mail, and other programs

eps

Encapsulated Postscript file

exe

Executable program file

flv

Flash-compatible video file

gif

Graphical Interchange Format file

htm, html

Hypertext markup language page

ini

Windows initialization configuration file

iso

ISO-9660 disc image

jar

Java architecture file

jpg, jpeg

Joint Photographic Experts Group photo file

m4a

MPEG-4 audio file

mdb

Microsoft Access database before Access 2007

mid, midi

Musical Instrument Digital Interface file

mov

Apple QuickTime movie file

mp3

MPEG layer 3 audio file

mp4

MPEG 4 video

mp4

MPEG 4 video

mpeg

Moving Picture Experts Group movie file

mpg

MPEG 1 system stream

msi

Microsoft installer file

mui

Multilingual User Interface file

pdf

Portable Document Format file

png

Portable Network Graphics file

pot

Microsoft PowerPoint template before PowerPoint 2007

potm

Microsoft PowerPoint macro-enabled template

potx

Microsoft PowerPoint template

ppam

Microsoft PowerPoint add-in

pps

Microsoft PowerPoint slideshow before PowerPoint 2007

ppsm

Microsoft PowerPoint macro-enabled slideshow

ppsx

Microsoft PowerPoint slideshow

ppt

Microsoft PowerPoint format before PowerPoint 2007

pptm

Microsoft PowerPoint macro-enabled presentation

pptx

Microsoft PowerPoint presentation

psd

Adobe Photoshop file

pst

Outlook data store

pub

Microsoft Publisher file

rar

Roshal Archive compressed file

rtf

Rich Text Format file

sldm

Microsoft PowerPoint macro-enabled slide

sldx

Microsoft PowerPoint slide

swf

Shockwave Flash file

sys

Microsoft DOS and Windows system settings and variables file

tif, tiff

Tagged Image Format file

tmp

Temporary data file

txt

Unformatted text file

vob

Video object file

vsd

Microsoft Visio drawing before Visio 2013

vsdm

Microsoft Visio macro-enabled drawing

vsdx

Microsoft Visio drawing file

vss

Microsoft Visio stencil before Visio 2013

vssm

Microsoft Visio macro-enabled stencil

vst

Microsoft Visio template before Visio 2013

vstm

Microsoft Visio macro-enabled template

vstx

Microsoft Visio template

wav

Wave audio file

wbk

Microsoft Word backup document

wks

Microsoft Works file

wma

Windows Media Audio file

wmd

Windows Media Download file

wmv

Windows Media Video file

wmz, wms

Windows Media skins file

wpd, wp5

WordPerfect document

xla

Microsoft Excel add-in or macro file

xlam

Microsoft Excel add-in after Excel 2007

xll

Microsoft Excel DLL-based add-in

xlm

Microsoft Excel macro before Excel 2007

xls

Microsoft Excel workbook before Excel 2007

xlsm

Microsoft Excel macro-enabled workbook after Excel 2007

xlsx

Microsoft Excel workbook after Excel 2007

xlt

Microsoft Excel template before Excel 2007

xltm

Microsoft Excel macro-enabled template after Excel 2007

xltx

Microsoft Excel template after Excel 2007

xps

XML-based document

zip

Compressed file

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