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

BAT file extension

DOS Batch File

Executable Files

CS file extension

Visual C# Source Code File

Developer Files

CUE file extension

Cue Sheet File

Disk Image Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

EPS file extension

Encapsulated PostScript File

Vector Image Files

HTML file extension

Hypertext Markup Language File

Web Files

KMZ file extension

Google Earth Placemark File

GIS Files

MAX file extension

3ds Max Scene File

3D Image Files

MSG file extension

Outlook Mail Message

Text Files

MSI file extension

Windows Installer Package

Misc Files

ODT file extension

OpenDocument Text Document

Text Files

TTF file extension

TrueType Font

Font Files

TXT file extension

Plain Text File

Text Files

UUE file extension

Uuencoded File

Encoded Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files