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

BAK file extension

Backup File

Backup Files

CS file extension

Visual C# Source Code File

Developer Files

DEB file extension

Debian Software Package

Compressed Files

FLA file extension

Adobe Flash Animation

Developer Files

GAM file extension

Saved Game File

Game Files

ICS file extension

iCalendar File

Misc Files

IFF file extension

Interchange File Format

Audio Files

LOG file extension

Log File

Text Files

M4A file extension

MPEG-4 Audio File

Audio Files

SAV file extension

Saved Game

Game Files

SWF file extension

Shockwave Flash Movie

Video Files

SYS file extension

Windows System File

System Files

THM file extension

Thumbnail Image File

Raster Image Files

TIF file extension

Tagged Image File

Raster Image Files

TOAST file extension

Toast Disc Image

Disk Image Files