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

CER file extension

Internet Security Certificate

Web Files

CGI file extension

Common Gateway Interface Script

Executable Files

DXF file extension

Drawing Exchange Format File

CAD Files

KML file extension

Keyhole Markup Language File

GIS Files

KMZ file extension

Google Earth Placemark File

GIS Files

MDB file extension

Microsoft Access Database

Database Files

MOBI file extension

Mobipocket eBook

eBook Files

MPG file extension

MPEG Video File

Video Files

MSG file extension

Outlook Mail Message

Text Files

PCT file extension

Picture File

Layout Files

PPT file extension

PowerPoint Presentation

Data Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

3GP file extension

3GPP Multimedia File

Video Files