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

ASP file extension

Active Server Page

Web Files

BAK file extension

Backup File

Backup Files

CLASS file extension

Java Class File

Developer Files

COM file extension

DOS Command File

Executable Files

DB file extension

Database File

Database Files

DOC file extension

Microsoft Word Document

Text Files

IFF file extension

Interchange File Format

Audio Files

LNK file extension

Windows File Shortcut

System Files

MID file extension

MIDI File

Audio Files

MPA file extension

MPEG-2 Audio File

Audio Files

MSG file extension

Outlook Mail Message

Text Files

MSI file extension

Windows Installer Package

Misc Files

PL file extension

Perl Script

Developer Files

SITX file extension

StuffIt X Archive

Compressed Files

TORRENT file extension

BitTorrent File

Misc Files