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

AIF file extension

Audio Interchange File Format

Audio Files

BAT file extension

DOS Batch File

Executable Files

CAB file extension

Windows Cabinet File

System Files

CSS file extension

Cascading Style Sheet

Web Files

M3U file extension

Media Playlist File

Audio Files

M4A file extension

MPEG-4 Audio File

Audio Files

M4V file extension

iTunes Video File

Video Files

MP4 file extension

MPEG-4 Video File

Video Files

OTF file extension

OpenType Font

Font Files

PHP file extension

PHP Source Code File

Web Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

SDF file extension

Standard Data File

Data Files

SLN file extension

Visual Studio Solution File

Developer Files

VOB file extension

DVD Video Object File

Video Files

3DM file extension

Rhino 3D Model

3D Image Files