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

RA file extension

Real Audio File

Audio Files

HTML file extension

Hypertext Markup Language File

Web Files

COM file extension

DOS Command File

Executable Files

M4V file extension

iTunes Video File

Video Files

THM file extension

Thumbnail Image File

Raster Image Files

PY file extension

Python Script

Developer Files

KEY file extension

Keynote Presentation

Data Files

DEB file extension

Debian Software Package

Compressed Files

FNT file extension

Windows Font File

Font Files

GPX file extension

GPS Exchange File

GIS Files

SYS file extension

Windows System File

System Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PRF file extension

Outlook Profile File

Settings Files

7Z file extension

7-Zip Compressed File

Compressed Files

DDS file extension

DirectDraw Surface

Raster Image Files