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

TXT file extension

Plain Text File

Text Files

FNT file extension

Windows Font File

Font Files

COM file extension

DOS Command File

Executable Files

FON file extension

Generic Font File

Font Files

SRT file extension

SubRip Subtitle File

Video Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

7Z file extension

7-Zip Compressed File

Compressed Files

RSS file extension

Rich Site Summary

Web Files

ICO file extension

Icon File

System Files

PRF file extension

Outlook Profile File

Settings Files

3GP file extension

3GPP Multimedia File

Video Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

TGA file extension

Targa Graphic

Raster Image Files

CSS file extension

Cascading Style Sheet

Web Files

ISO file extension

Disc Image File

Disk Image Files