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

CAB file extension

Windows Cabinet File

System Files

CSS file extension

Cascading Style Sheet

Web Files

CUE file extension

Cue Sheet File

Disk Image Files

DEB file extension

Debian Software Package

Compressed Files

FLA file extension

Adobe Flash Animation

Developer Files

ICS file extension

iCalendar File

Misc Files

IFF file extension

Interchange File Format

Audio Files

JSP file extension

Java Server Page

Web Files

KEY file extension

Keynote Presentation

Data Files

LNK file extension

Windows File Shortcut

System Files

M4V file extension

iTunes Video File

Video Files

PIF file extension

Program Information File

Executable Files

PPS file extension

PowerPoint Slide Show

Data Files

3GP file extension

3GPP Multimedia File

Video Files