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

ASPX file extension

Active Server Page Extended File

Web Files

BAK file extension

Backup File

Backup Files

DDS file extension

DirectDraw Surface

Raster Image Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

M4V file extension

iTunes Video File

Video Files

MAX file extension

3ds Max Scene File

3D Image Files

MP3 file extension

MP3 Audio File

Audio Files

MPG file extension

MPEG Video File

Video Files

OTF file extension

OpenType Font

Font Files

PDF file extension

Portable Document Format File

Layout Files

PS file extension

PostScript File

Vector Image Files

RSS file extension

Rich Site Summary

Web Files

TTF file extension

TrueType Font

Font Files

XCODEPROJ file extension

Xcode Project

Developer Files