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

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

DDS file extension

DirectDraw Surface

Raster Image Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

EXE file extension

Windows Executable File

Executable Files

HTML file extension

Hypertext Markup Language File

Web Files

MDF file extension

Media Disc Image File

Disk Image Files

PPT file extension

PowerPoint Presentation

Data Files

SITX file extension

StuffIt X Archive

Compressed Files

SYS file extension

Windows System File

System Files

THM file extension

Thumbnail Image File

Raster Image Files

VCF file extension

vCard File

Data Files

WPD file extension

WordPerfect Document

Text Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

3DM file extension

Rhino 3D Model

3D Image Files

3GP file extension

3GPP Multimedia File

Video Files