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

BAT file extension

DOS Batch File

Executable Files

CPP file extension

C++ Source Code File

Developer Files

DB file extension

Database File

Database Files

HTML file extension

Hypertext Markup Language File

Web Files

LNK file extension

Windows File Shortcut

System Files

M4V file extension

iTunes Video File

Video Files

MAX file extension

3ds Max Scene File

3D Image Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

PCT file extension

Picture File

Layout Files

RTF file extension

Rich Text Format File

Text Files

TARGZ file extension

Compressed Tarball File

Compressed Files

WPD file extension

WordPerfect Document

Text Files

XML file extension

XML File

Data Files

3G2 file extension

3GPP2 Multimedia File

Video Files