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

PHP file extension

PHP Source Code File

Web Files

CGI file extension

Common Gateway Interface Script

Executable Files

DTD file extension

Document Type Definition File

Developer Files

SLN file extension

Visual Studio Solution File

Developer Files

M4V file extension

iTunes Video File

Video Files

MDF file extension

Media Disc Image File

Disk Image Files

EPS file extension

Encapsulated PostScript File

Vector Image Files

SAV file extension

Saved Game

Game Files

CER file extension

Internet Security Certificate

Web Files

7Z file extension

7-Zip Compressed File

Compressed Files

PDF file extension

Portable Document Format File

Layout Files

KML file extension

Keyhole Markup Language File

GIS Files

TAR file extension

Consolidated Unix File Archive

Data Files

APP file extension

Mac OS X Application

Executable Files

RA file extension

Real Audio File

Audio Files