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

SYS file extension

Windows System File

System Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

WMV file extension

Windows Media Video File

Video Files

7Z file extension

7-Zip Compressed File

Compressed Files

MDB file extension

Microsoft Access Database

Database Files

TGA file extension

Targa Graphic

Raster Image Files

MDF file extension

Media Disc Image File

Disk Image Files

RSS file extension

Rich Site Summary

Web Files

KML file extension

Keyhole Markup Language File

GIS Files

CLASS file extension

Java Class File

Developer Files

EPUB file extension

Open eBook File

eBook Files

GED file extension

GEDCOM Genealogy Data File

Data Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

VCXPROJ file extension

Visual C++ Project

Developer Files

DWG file extension

AutoCAD Drawing Database File

CAD Files