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

CLASS file extension

Java Class File

Developer Files

COM file extension

DOS Command File

Executable Files

DBF file extension

Database File

Database Files

DLL file extension

Dynamic Link Library

System Files

DXF file extension

Drawing Exchange Format File

CAD Files

EPUB file extension

Open eBook File

eBook Files

KMZ file extension

Google Earth Placemark File

GIS Files

M4V file extension

iTunes Video File

Video Files

PHP file extension

PHP Source Code File

Web Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RM file extension

Real Media File

Video Files

SDF file extension

Standard Data File

Data Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

ZIPX file extension

Extended Zip File

Compressed Files