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

ASX file extension

Microsoft ASF Redirector File

Video Files

CPL file extension

Windows Control Panel Item

System Files

DAT file extension

Data File

Data Files

DDS file extension

DirectDraw Surface

Raster Image Files

GPX file extension

GPS Exchange File

GIS Files

ICNS file extension

Mac OS X Icon Resource File

System Files

M4V file extension

iTunes Video File

Video Files

MPG file extension

MPEG Video File

Video Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PPT file extension

PowerPoint Presentation

Data Files

RTF file extension

Rich Text Format File

Text Files

THM file extension

Thumbnail Image File

Raster Image Files

VCF file extension

vCard File

Data Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

3DS file extension

3D Studio Scene

3D Image Files