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

APK file extension

Android Package File

Executable Files

CSR file extension

Certificate Signing Request File

Web Files

CUR file extension

Windows Cursor

System Files

DEB file extension

Debian Software Package

Compressed Files

DRV file extension

Device Driver

System Files

GED file extension

GEDCOM Genealogy Data File

Data Files

MPG file extension

MPEG Video File

Video Files

MSI file extension

Windows Installer Package

Misc Files

PART file extension

Partially Downloaded File

Misc Files

PCT file extension

Picture File

Layout Files

PKG file extension

Mac OS X Installer Package

Compressed Files

SYS file extension

Windows System File

System Files

TXT file extension

Plain Text File

Text Files

WMV file extension

Windows Media Video File

Video Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files