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

ASX file extension

Microsoft ASF Redirector File

Video Files

AVI file extension

Audio Video Interleave File

Video Files

C file extension

C/C++ Source Code File

Developer Files

DOC file extension

Microsoft Word Document

Text Files

EXE file extension

Windows Executable File

Executable Files

FNT file extension

Windows Font File

Font Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

HTM file extension

Hypertext Markup Language File

Web Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

LUA file extension

Lua Source File

Developer Files

MAX file extension

3ds Max Scene File

3D Image Files

TOAST file extension

Toast Disc Image

Disk Image Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

3GP file extension

3GPP Multimedia File

Video Files