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

AVI file extension

Audio Video Interleave File

Video Files

CGI file extension

Common Gateway Interface Script

Executable Files

DBF file extension

Database File

Database Files

DOC file extension

Microsoft Word Document

Text Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

FNT file extension

Windows Font File

Font Files

FON file extension

Generic Font File

Font Files

IBOOKS file extension

Multi-Touch iBook

Data Files

MAX file extension

3ds Max Scene File

3D Image Files

PY file extension

Python Script

Developer Files

RSS file extension

Rich Site Summary

Web Files

SYS file extension

Windows System File

System Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

XML file extension

XML File

Data Files

ZIPX file extension

Extended Zip File

Compressed Files