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

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

7Z file extension

7-Zip Compressed File

Compressed Files

CER file extension

Internet Security Certificate

Web Files

CAB file extension

Windows Cabinet File

System Files

SAV file extension

Saved Game

Game Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

GED file extension

GEDCOM Genealogy Data File

Data Files

CBR file extension

Comic Book RAR Archive

Compressed Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

PHP file extension

PHP Source Code File

Web Files

SQL file extension

Structured Query Language Data File

Database Files

INDD file extension

Adobe InDesign Document

Layout Files

MID file extension

MIDI File

Audio Files

JSP file extension

Java Server Page

Web Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files