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

CLASS file extension

Java Class File

Developer Files

DAT file extension

Data File

Data Files

GPX file extension

GPS Exchange File

GIS Files

JPG file extension

JPEG Image

Raster Image Files

M3U file extension

Media Playlist File

Audio Files

MOBI file extension

Mobipocket eBook

eBook Files

MP3 file extension

MP3 Audio File

Audio Files

PNG file extension

Portable Network Graphic

Raster Image Files

PRF file extension

Outlook Profile File

Settings Files

RSS file extension

Rich Site Summary

Web Files

UUE file extension

Uuencoded File

Encoded Files

WSF file extension

Windows Script File

Executable Files

XCODEPROJ file extension

Xcode Project

Developer Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files