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

AVI file extension

Audio Video Interleave File

Video Files

CUE file extension

Cue Sheet File

Disk Image Files

DAT file extension

Data File

Data Files

FNT file extension

Windows Font File

Font Files

GPX file extension

GPS Exchange File

GIS Files

LNK file extension

Windows File Shortcut

System Files

MID file extension

MIDI File

Audio Files

NES file extension

Nintendo (NES) ROM File

Game Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PPS file extension

PowerPoint Slide Show

Data Files

SITX file extension

StuffIt X Archive

Compressed Files

SYS file extension

Windows System File

System Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

3G2 file extension

3GPP2 Multimedia File

Video Files