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

AI file extension

Adobe Illustrator File

Vector Image Files

AVI file extension

Audio Video Interleave File

Video Files

CER file extension

Internet Security Certificate

Web Files

CS file extension

Visual C# Source Code File

Developer Files

DBF file extension

Database File

Database Files

EPUB file extension

Open eBook File

eBook Files

FON file extension

Generic Font File

Font Files

ICO file extension

Icon File

System Files

INI file extension

Windows Initialization File

Settings Files

KEY file extension

Keynote Presentation

Data Files

MDB file extension

Microsoft Access Database

Database Files

PHP file extension

PHP Source Code File

Web Files

RA file extension

Real Audio File

Audio Files

RSS file extension

Rich Site Summary

Web Files

XCODEPROJ file extension

Xcode Project

Developer Files