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

CGI file extension

Common Gateway Interface Script

Executable Files

CLASS file extension

Java Class File

Developer Files

DBF file extension

Database File

Database Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

EXE file extension

Windows Executable File

Executable Files

GAM file extension

Saved Game File

Game Files

IBOOKS file extension

Multi-Touch iBook

Data Files

JS file extension

JavaScript File

Web Files

PDF file extension

Portable Document Format File

Layout Files

PPS file extension

PowerPoint Slide Show

Data Files

SDF file extension

Standard Data File

Data Files

SRT file extension

SubRip Subtitle File

Video Files

TMP file extension

Temporary File

Backup Files

VOB file extension

DVD Video Object File

Video Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files