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

AZW file extension

Amazon Kindle eBook File

eBook Files

CLASS file extension

Java Class File

Developer Files

COM file extension

DOS Command File

Executable Files

DOC file extension

Microsoft Word Document

Text Files

GED file extension

GEDCOM Genealogy Data File

Data Files

H file extension

C/C++/Objective-C Header File

Developer Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

JPG file extension

JPEG Image

Raster Image Files

KMZ file extension

Google Earth Placemark File

GIS Files

OTF file extension

OpenType Font

Font Files

PDF file extension

Portable Document Format File

Layout Files

PL file extension

Perl Script

Developer Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

RM file extension

Real Media File

Video Files

ZIPX file extension

Extended Zip File

Compressed Files