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

DMG file extension

Mac OS X Disk Image

Disk Image Files

ODT file extension

OpenDocument Text Document

Text Files

ICNS file extension

Mac OS X Icon Resource File

System Files

CBR file extension

Comic Book RAR Archive

Compressed Files

PCT file extension

Picture File

Layout Files

WSF file extension

Windows Script File

Executable Files

TEX file extension

LaTeX Source Document

Text Files

CUE file extension

Cue Sheet File

Disk Image Files

GBR file extension

Gerber File

Data Files

CER file extension

Internet Security Certificate

Web Files

JPG file extension

JPEG Image

Raster Image Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

7Z file extension

7-Zip Compressed File

Compressed Files

VCF file extension

vCard File

Data Files

THM file extension

Thumbnail Image File

Raster Image Files