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

CS file extension

Visual C# Source Code File

Developer Files

CSR file extension

Certificate Signing Request File

Web Files

CSS file extension

Cascading Style Sheet

Web Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

EPS file extension

Encapsulated PostScript File

Vector Image Files

PAGES file extension

Pages Document

Text Files

PDB file extension

Program Database

Database Files

PRF file extension

Outlook Profile File

Settings Files

RA file extension

Real Audio File

Audio Files

SDF file extension

Standard Data File

Data Files

THM file extension

Thumbnail Image File

Raster Image Files

UUE file extension

Uuencoded File

Encoded Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

3GP file extension

3GPP Multimedia File

Video Files