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

7Z file extension

7-Zip Compressed File

Compressed Files

FNT file extension

Windows Font File

Font Files

ACCDB file extension

Access 2007 Database File

Database Files

H file extension

C/C++/Objective-C Header File

Developer Files

XCODEPROJ file extension

Xcode Project

Developer Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PNG file extension

Portable Network Graphic

Raster Image Files

INDD file extension

Adobe InDesign Document

Layout Files

TARGZ file extension

Compressed Tarball File

Compressed Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

3DM file extension

Rhino 3D Model

3D Image Files

MDB file extension

Microsoft Access Database

Database Files

WPD file extension

WordPerfect Document

Text Files

PPS file extension

PowerPoint Slide Show

Data Files

MOV file extension

Apple QuickTime Movie

Video Files