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

CLASS file extension

Java Class File

Developer Files

MID file extension

MIDI File

Audio Files

ZIPX file extension

Extended Zip File

Compressed Files

TIF file extension

Tagged Image File

Raster Image Files

LUA file extension

Lua Source File

Developer Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

M4V file extension

iTunes Video File

Video Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

CSR file extension

Certificate Signing Request File

Web Files

MPG file extension

MPEG Video File

Video Files

MSI file extension

Windows Installer Package

Misc Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

CSV file extension

Comma Separated Values File

Data Files

TTF file extension

TrueType Font

Font Files