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

APP file extension

Mac OS X Application

Executable Files

CAB file extension

Windows Cabinet File

System Files

CER file extension

Internet Security Certificate

Web Files

CUE file extension

Cue Sheet File

Disk Image Files

DB file extension

Database File

Database Files

DOC file extension

Microsoft Word Document

Text Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

MDB file extension

Microsoft Access Database

Database Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

MOV file extension

Apple QuickTime Movie

Video Files

PL file extension

Perl Script

Developer Files

RSS file extension

Rich Site Summary

Web Files

VCF file extension

vCard File

Data Files

WAV file extension

WAVE Audio File

Audio Files

ZIPX file extension

Extended Zip File

Compressed Files