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

CSR file extension

Certificate Signing Request File

Web Files

DB file extension

Database File

Database Files

DLL file extension

Dynamic Link Library

System Files

H file extension

C/C++/Objective-C Header File

Developer Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

JAR file extension

Java Archive File

Executable Files

M4V file extension

iTunes Video File

Video Files

MPG file extension

MPEG Video File

Video Files

RM file extension

Real Media File

Video Files

RSS file extension

Rich Site Summary

Web 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

TTF file extension

TrueType Font

Font Files