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

DOCX file extension

Microsoft Word Open XML Document

Text Files

PPS file extension

PowerPoint Slide Show

Data Files

PRF file extension

Outlook Profile File

Settings Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

FLA file extension

Adobe Flash Animation

Developer Files

CSS file extension

Cascading Style Sheet

Web Files

PAGES file extension

Pages Document

Text Files

7Z file extension

7-Zip Compressed File

Compressed Files

MOBI file extension

Mobipocket eBook

eBook Files

PNG file extension

Portable Network Graphic

Raster Image Files

SRT file extension

SubRip Subtitle File

Video Files

RSS file extension

Rich Site Summary

Web Files

SYS file extension

Windows System File

System Files

TXT file extension

Plain Text File

Text Files

ROM file extension

N64 Game ROM File

Game Files