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

BMP file extension

Bitmap Image File

Raster Image Files

CRX file extension

Chrome Extension

Plugin Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

HTML file extension

Hypertext Markup Language File

Web Files

ISO file extension

Disc Image File

Disk Image Files

MDB file extension

Microsoft Access Database

Database Files

MSG file extension

Outlook Mail Message

Text Files

MSI file extension

Windows Installer Package

Misc Files

NES file extension

Nintendo (NES) ROM File

Game Files

PDF file extension

Portable Document Format File

Layout Files

PHP file extension

PHP Source Code File

Web Files

RM file extension

Real Media File

Video Files

TMP file extension

Temporary File

Backup Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

YUV file extension

YUV Encoded Image File

Raster Image Files