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

7Z file extension

7-Zip Compressed File

Compressed Files

RM file extension

Real Media File

Video Files

DBF file extension

Database File

Database Files

PCT file extension

Picture File

Layout Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

RSS file extension

Rich Site Summary

Web Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

THM file extension

Thumbnail Image File

Raster Image Files

CLASS file extension

Java Class File

Developer Files

IBOOKS file extension

Multi-Touch iBook

Data Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

EPUB file extension

Open eBook File

eBook Files

CAB file extension

Windows Cabinet File

System Files

ASF file extension

Advanced Systems Format File

Video Files

AIF file extension

Audio Interchange File Format

Audio Files