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

CAB file extension

Windows Cabinet File

System Files

CGI file extension

Common Gateway Interface Script

Executable Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

EPUB file extension

Open eBook File

eBook Files

GZ file extension

Gnu Zipped Archive

Compressed Files

IFF file extension

Interchange File Format

Audio Files

JS file extension

JavaScript File

Web Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PPS file extension

PowerPoint Slide Show

Data Files

RSS file extension

Rich Site Summary

Web Files

SRT file extension

SubRip Subtitle File

Video Files

TIFF file extension

Tagged Image File Format

Raster Image Files

VCD file extension

Virtual CD

Disk Image Files

WMA file extension

Windows Media Audio File

Audio Files