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

AIF file extension

Audio Interchange File Format

Audio Files

CS file extension

Visual C# Source Code File

Developer Files

DEB file extension

Debian Software Package

Compressed Files

FNT file extension

Windows Font File

Font Files

FON file extension

Generic Font File

Font Files

H file extension

C/C++/Objective-C Header File

Developer Files

ICNS file extension

Mac OS X Icon Resource File

System Files

MID file extension


Audio Files

MP3 file extension

MP3 Audio File

Audio Files

PHP file extension

PHP Source Code File

Web Files

PL file extension

Perl Script

Developer Files

PPT file extension

PowerPoint Presentation

Data Files

UUE file extension

Uuencoded File

Encoded Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

ZIP file extension

Zipped File

Compressed Files