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

ASPX file extension

Active Server Page Extended File

Web Files

COM file extension

DOS Command File

Executable Files

GAM file extension

Saved Game File

Game Files

ICS file extension

iCalendar File

Misc Files

IFF file extension

Interchange File Format

Audio Files

MAX file extension

3ds Max Scene File

3D Image Files

MDF file extension

Media Disc Image File

Disk Image Files

MID file extension

MIDI File

Audio Files

ODT file extension

OpenDocument Text Document

Text Files

PCT file extension

Picture File

Layout Files

RM file extension

Real Media File

Video Files

TARGZ file extension

Compressed Tarball File

Compressed Files

WSF file extension

Windows Script File

Executable Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

3G2 file extension

3GPP2 Multimedia File

Video Files