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

DBF file extension

Database File

Database Files

7Z file extension

7-Zip Compressed File

Compressed Files

IFF file extension

Interchange File Format

Audio Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

JPG file extension

JPEG Image

Raster Image Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PDF file extension

Portable Document Format File

Layout Files

DXF file extension

Drawing Exchange Format File

CAD Files

WPD file extension

WordPerfect Document

Text Files

CSS file extension

Cascading Style Sheet

Web Files

TXT file extension

Plain Text File

Text Files

PART file extension

Partially Downloaded File

Misc Files

CLASS file extension

Java Class File

Developer Files

DTD file extension

Document Type Definition File

Developer Files