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

AIF file extension

Audio Interchange File Format

Audio Files

CAB file extension

Windows Cabinet File

System Files

CPP file extension

C++ Source Code File

Developer Files

CSR file extension

Certificate Signing Request File

Web Files

CSS file extension

Cascading Style Sheet

Web Files

CUR file extension

Windows Cursor

System Files

DB file extension

Database File

Database Files

DDS file extension

DirectDraw Surface

Raster Image Files

HTML file extension

Hypertext Markup Language File

Web Files

ICNS file extension

Mac OS X Icon Resource File

System Files

LNK file extension

Windows File Shortcut

System Files

PY file extension

Python Script

Developer Files

RTF file extension

Rich Text Format File

Text Files

SLN file extension

Visual Studio Solution File

Developer Files

WMV file extension

Windows Media Video File

Video Files