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

PAGES file extension

Pages Document

Text Files

GPX file extension

GPS Exchange File

GIS Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

INI file extension

Windows Initialization File

Settings Files

PHP file extension

PHP Source Code File

Web Files

PRF file extension

Outlook Profile File

Settings Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

CLASS file extension

Java Class File

Developer Files

ASX file extension

Microsoft ASF Redirector File

Video Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

7Z file extension

7-Zip Compressed File

Compressed Files

JS file extension

JavaScript File

Web Files

PDB file extension

Program Database

Database Files

WAV file extension

WAVE Audio File

Audio Files

3DM file extension

Rhino 3D Model

3D Image Files