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

CFG file extension

Configuration File

Settings Files

CSR file extension

Certificate Signing Request File

Web Files

DOC file extension

Microsoft Word Document

Text Files

FON file extension

Generic Font File

Font Files

KEY file extension

Keynote Presentation

Data Files

M4A file extension

MPEG-4 Audio File

Audio Files

MDB file extension

Microsoft Access Database

Database Files

MSI file extension

Windows Installer Package

Misc Files

PRF file extension

Outlook Profile File

Settings Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

SITX file extension

StuffIt X Archive

Compressed Files

SLN file extension

Visual Studio Solution File

Developer Files

TARGZ file extension

Compressed Tarball File

Compressed Files

VOB file extension

DVD Video Object File

Video Files

XLR file extension

Works Spreadsheet

Spreadsheet Files