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

CSS file extension

Cascading Style Sheet

Web Files

DRV file extension

Device Driver

System Files

DXF file extension

Drawing Exchange Format File

CAD Files

EPUB file extension

Open eBook File

eBook Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

IBOOKS file extension

Multi-Touch iBook

Data Files

JS file extension

JavaScript File

Web Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

M3U file extension

Media Playlist File

Audio Files

M4A file extension

MPEG-4 Audio File

Audio Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

PY file extension

Python Script

Developer Files

SLN file extension

Visual Studio Solution File

Developer Files

VOB file extension

DVD Video Object File

Video Files

YUV file extension

YUV Encoded Image File

Raster Image Files