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

C file extension

C/C++ Source Code File

Developer Files

CAB file extension

Windows Cabinet File

System Files

CER file extension

Internet Security Certificate

Web Files

CFM file extension

ColdFusion Markup File

Web Files

CS file extension

Visual C# Source Code File

Developer Files

CUR file extension

Windows Cursor

System Files

DEB file extension

Debian Software Package

Compressed Files

JSP file extension

Java Server Page

Web Files

MOV file extension

Apple QuickTime Movie

Video Files

MP4 file extension

MPEG-4 Video File

Video Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

TARGZ file extension

Compressed Tarball File

Compressed Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

XML file extension

XML File

Data Files