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

CER file extension

Internet Security Certificate

Web Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

FNT file extension

Windows Font File

Font Files

ICS file extension

iCalendar File

Misc Files

JAR file extension

Java Archive File

Executable Files

MAX file extension

3ds Max Scene File

3D Image Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PPT file extension

PowerPoint Presentation

Data Files

RM file extension

Real Media File

Video Files

SYS file extension

Windows System File

System Files

TAR file extension

Consolidated Unix File Archive

Data Files

TORRENT file extension

BitTorrent File

Misc Files

VB file extension

VBScript File

Executable Files

WMV file extension

Windows Media Video File

Video Files

3G2 file extension

3GPP2 Multimedia File

Video Files