File extensions – definition and basic information


File extensions are the integral parts of the files that are on each computer. Often, when working on a computer, we encounter a wide range of files, such as docx, ppt, part, mp3 or rmvb. We realize that they are there – but we often do not know what they are for on our computer.

File extension, also known as the filename extension is a suffix added to the name of a computer file, usually consisting of a number of characters placed after the last dot in the filename, which gives us information about its coding. In other words a file extension is a file format. It allows the operating system (e.g. Windows) to recognize what program it should try to open the file.

In the table below you will find a random selection of popular file extensions.


File extension The full name of the file Category

CUR file extension

Windows Cursor

System Files

MAX file extension

3ds Max Scene File

3D Image Files

MSG file extension

Outlook Mail Message

Text Files

AVI file extension

Audio Video Interleave File

Video Files

CSR file extension

Certificate Signing Request File

Web Files

ASPX file extension

Active Server Page Extended File

Web Files

LNK file extension

Windows File Shortcut

System Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

FLV file extension

Flash Video File

Video Files

PAGES file extension

Pages Document

Text Files

7Z file extension

7-Zip Compressed File

Compressed Files

BAT file extension

DOS Batch File

Executable Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

APK file extension

Android Package File

Executable Files

CLASS file extension

Java Class File

Developer Files