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

M4A file extension

MPEG-4 Audio File

Audio Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

JS file extension

JavaScript File

Web Files

CLASS file extension

Java Class File

Developer Files

ASF file extension

Advanced Systems Format File

Video Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

ASPX file extension

Active Server Page Extended File

Web Files

APP file extension

Mac OS X Application

Executable Files

CUE file extension

Cue Sheet File

Disk Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

EPUB file extension

Open eBook File

eBook Files

JAR file extension

Java Archive File

Executable Files

APK file extension

Android Package File

Executable Files

TORRENT file extension

BitTorrent File

Misc Files

DB file extension

Database File

Database Files