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

ASF file extension

Advanced Systems Format File

Video Files

DEM file extension

Video Game Demo File

Game Files

EPUB file extension

Open eBook File

eBook Files

FNT file extension

Windows Font File

Font Files

INDD file extension

Adobe InDesign Document

Layout Files

LUA file extension

Lua Source File

Developer Files

M3U file extension

Media Playlist File

Audio Files

MOBI file extension

Mobipocket eBook

eBook Files

OTF file extension

OpenType Font

Font Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

RM file extension

Real Media File

Video Files

TIFF file extension

Tagged Image File Format

Raster Image Files

TMP file extension

Temporary File

Backup Files

VOB file extension

DVD Video Object File

Video Files

3DS file extension

3D Studio Scene

3D Image Files