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

ODT file extension

OpenDocument Text Document

Text Files

APP file extension

Mac OS X Application

Executable Files

KMZ file extension

Google Earth Placemark File

GIS Files

THM file extension

Thumbnail Image File

Raster Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

MP3 file extension

MP3 Audio File

Audio Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

RSS file extension

Rich Site Summary

Web Files

DDS file extension

DirectDraw Surface

Raster Image Files

RM file extension

Real Media File

Video Files

PPT file extension

PowerPoint Presentation

Data Files

MPA file extension

MPEG-2 Audio File

Audio Files

RTF file extension

Rich Text Format File

Text Files

CRX file extension

Chrome Extension

Plugin Files

LUA file extension

Lua Source File

Developer Files