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

ASX file extension

Microsoft ASF Redirector File

Video Files

CFG file extension

Configuration File

Settings Files

CUR file extension

Windows Cursor

System Files

DOC# file extension

Microsoft Word Document

Text Files

FLV file extension

Flash Video File

Video Files

FNT file extension

Windows Font File

Font Files

INDD file extension

Adobe InDesign Document

Layout Files

KML file extension

Keyhole Markup Language File

GIS Files

LOG file extension

Log File

Text Files

MPG file extension

MPEG Video File

Video Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PDF file extension

Portable Document Format File

Layout Files

PIF file extension

Program Information File

Executable Files

PNG file extension

Portable Network Graphic

Raster Image Files

PPT file extension

PowerPoint Presentation

Data Files