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

DEB file extension

Debian Software Package

Compressed Files

ASF file extension

Advanced Systems Format File

Video Files

ROM file extension

N64 Game ROM File

Game Files

TMP file extension

Temporary File

Backup Files

AI file extension

Adobe Illustrator File

Vector Image Files

KML file extension

Keyhole Markup Language File

GIS Files

WPD file extension

WordPerfect Document

Text Files

PDF file extension

Portable Document Format File

Layout Files

KEY file extension

Keynote Presentation

Data Files

AZW file extension

Amazon Kindle eBook File

eBook Files

DLL file extension

Dynamic Link Library

System Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

7Z file extension

7-Zip Compressed File

Compressed Files

MP3 file extension

MP3 Audio File

Audio Files

MSG file extension

Outlook Mail Message

Text Files