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

ASF file extension

Advanced Systems Format File

Video Files

C file extension

C/C++ Source Code File

Developer Files

CFG file extension

Configuration File

Settings Files

DEB file extension

Debian Software Package

Compressed Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

GED file extension

GEDCOM Genealogy Data File

Data Files

INI file extension

Windows Initialization File

Settings Files

MP3 file extension

MP3 Audio File

Audio Files

PCT file extension

Picture File

Layout Files

RA file extension

Real Audio File

Audio Files

UUE file extension

Uuencoded File

Encoded Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

ZIPX file extension

Extended Zip File

Compressed Files

3DM file extension

Rhino 3D Model

3D Image Files