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

C file extension

C/C++ Source Code File

Developer Files

CAB file extension

Windows Cabinet File

System Files

CPP file extension

C++ Source Code File

Developer Files

CRX file extension

Chrome Extension

Plugin Files

CUE file extension

Cue Sheet File

Disk Image Files

DAT file extension

Data File

Data Files

DEM file extension

Video Game Demo File

Game Files

DTD file extension

Document Type Definition File

Developer Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

FNT file extension

Windows Font File

Font Files

LNK file extension

Windows File Shortcut

System Files

LUA file extension

Lua Source File

Developer Files

PDF file extension

Portable Document Format File

Layout Files

SWF file extension

Shockwave Flash Movie

Video Files

XLR file extension

Works Spreadsheet

Spreadsheet Files