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

ASP file extension

Active Server Page

Web Files

BAK file extension

Backup File

Backup Files

CAB file extension

Windows Cabinet File

System Files

DEB file extension

Debian Software Package

Compressed Files

DRV file extension

Device Driver

System Files

ICNS file extension

Mac OS X Icon Resource File

System Files

JSP file extension

Java Server Page

Web Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

MP4 file extension

MPEG-4 Video File

Video Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RA file extension

Real Audio File

Audio Files

TIF file extension

Tagged Image File

Raster Image Files