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

CAB file extension

Windows Cabinet File

System Files

WAV file extension

WAVE Audio File

Audio Files

LOG file extension

Log File

Text Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

APK file extension

Android Package File

Executable Files

DB file extension

Database File

Database Files

MDF file extension

Media Disc Image File

Disk Image Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

FLV file extension

Flash Video File

Video Files

ASPX file extension

Active Server Page Extended File

Web Files

KEY file extension

Keynote Presentation

Data Files

PKG file extension

Mac OS X Installer Package

Compressed Files

DEB file extension

Debian Software Package

Compressed Files

MOBI file extension

Mobipocket eBook

eBook Files