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

AIF file extension

Audio Interchange File Format

Audio Files

APK file extension

Android Package File

Executable Files

CAB file extension

Windows Cabinet File

System Files

GADGET file extension

Windows Gadget

Executable Files

MOV file extension

Apple QuickTime Movie

Video Files

MPG file extension

MPEG Video File

Video Files

MSG file extension

Outlook Mail Message

Text Files

MSI file extension

Windows Installer Package

Misc Files

PDB file extension

Program Database

Database Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

RTF file extension

Rich Text Format File

Text Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

ZIPX file extension

Extended Zip File

Compressed Files

3DS file extension

3D Studio Scene

3D Image Files

3G2 file extension

3GPP2 Multimedia File

Video Files