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

AI file extension

Adobe Illustrator File

Vector Image Files

AIF file extension

Audio Interchange File Format

Audio Files

CSS file extension

Cascading Style Sheet

Web Files

CUR file extension

Windows Cursor

System Files

DTD file extension

Document Type Definition File

Developer Files

GZ file extension

Gnu Zipped Archive

Compressed Files

ICNS file extension

Mac OS X Icon Resource File

System Files

JS file extension

JavaScript File

Web Files

KML file extension

Keyhole Markup Language File

GIS Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

SITX file extension

StuffIt X Archive

Compressed Files

SQL file extension

Structured Query Language Data File

Database Files

TIFF file extension

Tagged Image File Format

Raster Image Files

YUV file extension

YUV Encoded Image File

Raster Image Files

3GP file extension

3GPP Multimedia File

Video Files