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

ASF file extension

Advanced Systems Format File

Video Files

ASPX file extension

Active Server Page Extended File

Web Files

ASX file extension

Microsoft ASF Redirector File

Video Files

CAB file extension

Windows Cabinet File

System Files

FON file extension

Generic Font File

Font Files

IBOOKS file extension

Multi-Touch iBook

Data Files

ISO file extension

Disc Image File

Disk Image Files

M4A file extension

MPEG-4 Audio File

Audio Files

MPG file extension

MPEG Video File

Video Files

PART file extension

Partially Downloaded File

Misc Files

PCT file extension

Picture File

Layout Files

PY file extension

Python Script

Developer Files

SQL file extension

Structured Query Language Data File

Database Files

WPS file extension

Microsoft Works Word Processor Document

Text Files