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

INDD file extension

Adobe InDesign Document

Layout Files

GBR file extension

Gerber File

Data Files

MP3 file extension

MP3 Audio File

Audio Files

DDS file extension

DirectDraw Surface

Raster Image Files

HTM file extension

Hypertext Markup Language File

Web Files

MOV file extension

Apple QuickTime Movie

Video Files

TIF file extension

Tagged Image File

Raster Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

IFF file extension

Interchange File Format

Audio Files

AVI file extension

Audio Video Interleave File

Video Files

PNG file extension

Portable Network Graphic

Raster Image Files

SLN file extension

Visual Studio Solution File

Developer Files

MP4 file extension

MPEG-4 Video File

Video Files

XML file extension

XML File

Data Files

3GP file extension

3GPP Multimedia File

Video Files