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

APP file extension

Mac OS X Application

Executable Files

ASP file extension

Active Server Page

Web Files

BAT file extension

DOS Batch File

Executable Files

CAB file extension

Windows Cabinet File

System Files

CSR file extension

Certificate Signing Request File

Web Files

DEM file extension

Video Game Demo File

Game Files

IFF file extension

Interchange File Format

Audio Files

INDD file extension

Adobe InDesign Document

Layout Files

LUA file extension

Lua Source File

Developer Files

MP3 file extension

MP3 Audio File

Audio Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

RPM file extension

Red Hat Package Manager File

Compressed Files

TAR file extension

Consolidated Unix File Archive

Data Files

TMP file extension

Temporary File

Backup Files

XLR file extension

Works Spreadsheet

Spreadsheet Files