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

AI file extension

Adobe Illustrator File

Vector Image Files

AVI file extension

Audio Video Interleave File

Video Files

BMP file extension

Bitmap Image File

Raster Image Files

DB file extension

Database File

Database Files

DNG file extension

Digital Negative Image File

Camera Raw Files

DTD file extension

Document Type Definition File

Developer Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

ICS file extension

iCalendar File

Misc Files

M3U file extension

Media Playlist File

Audio Files

M4A file extension

MPEG-4 Audio File

Audio Files

PDB file extension

Program Database

Database Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

RM file extension

Real Media File

Video Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

3G2 file extension

3GPP2 Multimedia File

Video Files