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

CFM file extension

ColdFusion Markup File

Web Files

DAT file extension

Data File

Data Files

DMP file extension

Windows Memory Dump

System Files

M4A file extension

MPEG-4 Audio File

Audio Files

PAGES file extension

Pages Document

Text Files

PCT file extension

Picture File

Layout Files

PS file extension

PostScript File

Vector Image Files

PY file extension

Python Script

Developer Files

RTF file extension

Rich Text Format File

Text Files

VCF file extension

vCard File

Data Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

3DM file extension

Rhino 3D Model

3D Image Files

3G2 file extension

3GPP2 Multimedia File

Video Files