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

APK file extension

Android Package File

Executable Files

AZW file extension

Amazon Kindle eBook File

eBook Files

CFM file extension

ColdFusion Markup File

Web Files

CSR file extension

Certificate Signing Request File

Web Files

CSS file extension

Cascading Style Sheet

Web Files

DTD file extension

Document Type Definition File

Developer Files

EXE file extension

Windows Executable File

Executable Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MPG file extension

MPEG Video File

Video Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RTF file extension

Rich Text Format File

Text Files

SYS file extension

Windows System File

System Files

TGA file extension

Targa Graphic

Raster Image Files

VCF file extension

vCard File

Data Files

WSF file extension

Windows Script File

Executable Files