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

TAR file extension

Consolidated Unix File Archive

Data Files

SYS file extension

Windows System File

System Files

AI file extension

Adobe Illustrator File

Vector Image Files

WSF file extension

Windows Script File

Executable Files

MP4 file extension

MPEG-4 Video File

Video Files

PDF file extension

Portable Document Format File

Layout Files

DB file extension

Database File

Database Files

NES file extension

Nintendo (NES) ROM File

Game Files

APP file extension

Mac OS X Application

Executable Files

CPL file extension

Windows Control Panel Item

System Files

RPM file extension

Red Hat Package Manager File

Compressed Files

CUE file extension

Cue Sheet File

Disk Image Files

SRT file extension

SubRip Subtitle File

Video Files

TOAST file extension

Toast Disc Image

Disk Image Files

7Z file extension

7-Zip Compressed File

Compressed Files