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

AI file extension

Adobe Illustrator File

Vector Image Files

AIF file extension

Audio Interchange File Format

Audio Files

CSR file extension

Certificate Signing Request File

Web Files

CUE file extension

Cue Sheet File

Disk Image Files

DTD file extension

Document Type Definition File

Developer Files

FNT file extension

Windows Font File

Font Files

GAM file extension

Saved Game File

Game Files

MP4 file extension

MPEG-4 Video File

Video Files

PCT file extension

Picture File

Layout Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

SITX file extension

StuffIt X Archive

Compressed Files

SWF file extension

Shockwave Flash Movie

Video Files

VCF file extension

vCard File

Data Files

XML file extension

XML File

Data Files

ZIPX file extension

Extended Zip File

Compressed Files