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

CSS file extension

Cascading Style Sheet

Web Files

DEM file extension

Video Game Demo File

Game Files

DOC# file extension

Microsoft Word Document

Text Files

FLA file extension

Adobe Flash Animation

Developer Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

LOG file extension

Log File

Text Files

MSI file extension

Windows Installer Package

Misc Files

PDF file extension

Portable Document Format File

Layout Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RTF file extension

Rich Text Format File

Text Files

TARGZ file extension

Compressed Tarball File

Compressed Files

TEX file extension

LaTeX Source Document

Text Files

TORRENT file extension

BitTorrent File

Misc Files

3GP file extension

3GPP Multimedia File

Video Files