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

APP file extension

Mac OS X Application

Executable Files

AZW file extension

Amazon Kindle eBook File

eBook Files

BAT file extension

DOS Batch File

Executable Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

DRV file extension

Device Driver

System Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

IFF file extension

Interchange File Format

Audio Files

MAX file extension

3ds Max Scene File

3D Image Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

UUE file extension

Uuencoded File

Encoded Files

VCXPROJ file extension

Visual C++ Project

Developer Files

XCODEPROJ file extension

Xcode Project

Developer Files

3DM file extension

Rhino 3D Model

3D Image Files

3GP file extension

3GPP Multimedia File

Video Files