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

PDF file extension

Portable Document Format File

Layout Files

PPT file extension

PowerPoint Presentation

Data Files

MOBI file extension

Mobipocket eBook

eBook Files

MP4 file extension

MPEG-4 Video File

Video Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

M3U file extension

Media Playlist File

Audio Files

VCXPROJ file extension

Visual C++ Project

Developer Files

AZW file extension

Amazon Kindle eBook File

eBook Files

MP3 file extension

MP3 Audio File

Audio Files

DEB file extension

Debian Software Package

Compressed Files

CSS file extension

Cascading Style Sheet

Web Files

GADGET file extension

Windows Gadget

Executable Files

7Z file extension

7-Zip Compressed File

Compressed Files

ICNS file extension

Mac OS X Icon Resource File

System Files

EPUB file extension

Open eBook File

eBook Files