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

AZW file extension

Amazon Kindle eBook File

eBook Files

CFG file extension

Configuration File

Settings Files

CRX file extension

Chrome Extension

Plugin Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

DTD file extension

Document Type Definition File

Developer Files

GBR file extension

Gerber File

Data Files

HTM file extension

Hypertext Markup Language File

Web Files

JS file extension

JavaScript File

Web Files

MDF file extension

Media Disc Image File

Disk Image Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

PL file extension

Perl Script

Developer Files

PPT file extension

PowerPoint Presentation

Data Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

3DM file extension

Rhino 3D Model

3D Image Files