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

3DS file extension

3D Studio Scene

3D Image Files

KEY file extension

Keynote Presentation

Data Files

PDF file extension

Portable Document Format File

Layout Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

CSS file extension

Cascading Style Sheet

Web Files

CSV file extension

Comma Separated Values File

Data Files

CS file extension

Visual C# Source Code File

Developer Files

TAR file extension

Consolidated Unix File Archive

Data Files

GAM file extension

Saved Game File

Game Files

ASP file extension

Active Server Page

Web Files

DLL file extension

Dynamic Link Library

System Files

7Z file extension

7-Zip Compressed File

Compressed Files

DOC# file extension

Microsoft Word Document

Text Files

LOG file extension

Log File

Text Files

WSF file extension

Windows Script File

Executable Files