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

AIF file extension

Audio Interchange File Format

Audio Files

BAK file extension

Backup File

Backup Files

CGI file extension

Common Gateway Interface Script

Executable Files

GPX file extension

GPS Exchange File

GIS Files

INDD file extension

Adobe InDesign Document

Layout Files

LOG file extension

Log File

Text Files

MDF file extension

Media Disc Image File

Disk Image Files

NES file extension

Nintendo (NES) ROM File

Game Files

PIF file extension

Program Information File

Executable Files

PS file extension

PostScript File

Vector Image Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

SAV file extension

Saved Game

Game Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

3DM file extension

Rhino 3D Model

3D Image Files