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

ASX file extension

Microsoft ASF Redirector File

Video Files

CBR file extension

Comic Book RAR Archive

Compressed Files

CER file extension

Internet Security Certificate

Web Files

CUR file extension

Windows Cursor

System Files

DNG file extension

Digital Negative Image File

Camera Raw Files

DOC file extension

Microsoft Word Document

Text Files

DOC# file extension

Microsoft Word Document

Text Files

FON file extension

Generic Font File

Font Files

ICNS file extension

Mac OS X Icon Resource File

System Files

JS file extension

JavaScript File

Web Files

PY file extension

Python Script

Developer Files

TTF file extension

TrueType Font

Font Files

WMV file extension

Windows Media Video File

Video Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

ZIP file extension

Zipped File

Compressed Files