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

AZW file extension

Amazon Kindle eBook File

eBook Files

BMP file extension

Bitmap Image File

Raster Image Files

CFM file extension

ColdFusion Markup File

Web Files

CPP file extension

C++ Source Code File

Developer Files

CUE file extension

Cue Sheet File

Disk Image Files

DLL file extension

Dynamic Link Library

System Files

IFF file extension

Interchange File Format

Audio Files

MAX file extension

3ds Max Scene File

3D Image Files

MP4 file extension

MPEG-4 Video File

Video Files

OTF file extension

OpenType Font

Font Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

RM file extension

Real Media File

Video Files

RSS file extension

Rich Site Summary

Web Files

SITX file extension

StuffIt X Archive

Compressed Files

UUE file extension

Uuencoded File

Encoded Files