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

CFM file extension

ColdFusion Markup File

Web Files

CUR file extension

Windows Cursor

System Files

DAT file extension

Data File

Data Files

ICO file extension

Icon File

System Files

KEY file extension

Keynote Presentation

Data Files

MDB file extension

Microsoft Access Database

Database Files

MSG file extension

Outlook Mail Message

Text Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PPT file extension

PowerPoint Presentation

Data Files

PS file extension

PostScript File

Vector Image Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

TOAST file extension

Toast Disc Image

Disk Image Files

TXT file extension

Plain Text File

Text Files

XCODEPROJ file extension

Xcode Project

Developer Files

XML file extension

XML File

Data Files