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

ASPX file extension

Active Server Page Extended File

Web Files

AVI file extension

Audio Video Interleave File

Video Files

CRX file extension

Chrome Extension

Plugin Files

CS file extension

Visual C# Source Code File

Developer Files

DEB file extension

Debian Software Package

Compressed Files

DNG file extension

Digital Negative Image File

Camera Raw Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

GZ file extension

Gnu Zipped Archive

Compressed Files

MAX file extension

3ds Max Scene File

3D Image Files

MP4 file extension

MPEG-4 Video File

Video Files

TTF file extension

TrueType Font

Font Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

XCODEPROJ file extension

Xcode Project

Developer Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files