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

VOB file extension

DVD Video Object File

Video Files

TTF file extension

TrueType Font

Font Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

LNK file extension

Windows File Shortcut

System Files

WMA file extension

Windows Media Audio File

Audio Files

FNT file extension

Windows Font File

Font Files

CLASS file extension

Java Class File

Developer Files

DXF file extension

Drawing Exchange Format File

CAD Files

CSS file extension

Cascading Style Sheet

Web Files

PART file extension

Partially Downloaded File

Misc Files

ISO file extension

Disc Image File

Disk Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

MP3 file extension

MP3 Audio File

Audio Files

INDD file extension

Adobe InDesign Document

Layout Files

MAX file extension

3ds Max Scene File

3D Image Files