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

ASP file extension

Active Server Page

Web Files

C file extension

C/C++ Source Code File

Developer Files

CUR file extension

Windows Cursor

System Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

H file extension

C/C++/Objective-C Header File

Developer Files

KEY file extension

Keynote Presentation

Data Files

M4A file extension

MPEG-4 Audio File

Audio Files

PHP file extension

PHP Source Code File

Web Files

PS file extension

PostScript File

Vector Image Files

VCD file extension

Virtual CD

Disk Image Files

VCF file extension

vCard File

Data Files

WSF file extension

Windows Script File

Executable Files

XCODEPROJ file extension

Xcode Project

Developer Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files