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

CLASS file extension

Java Class File

Developer Files

GED file extension

GEDCOM Genealogy Data File

Data Files

H file extension

C/C++/Objective-C Header File

Developer Files

KEY file extension

Keynote Presentation

Data Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

LUA file extension

Lua Source File

Developer Files

PART file extension

Partially Downloaded File

Misc Files

PDB file extension

Program Database

Database Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

TEX file extension

LaTeX Source Document

Text Files

TOAST file extension

Toast Disc Image

Disk Image Files

WPD file extension

WordPerfect Document

Text Files

ZIP file extension

Zipped File

Compressed Files

3DM file extension

Rhino 3D Model

3D Image Files