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

CER file extension

Internet Security Certificate

Web Files

COM file extension

DOS Command File

Executable Files

CS file extension

Visual C# Source Code File

Developer Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

GED file extension

GEDCOM Genealogy Data File

Data Files

GPX file extension

GPS Exchange File

GIS Files

MAX file extension

3ds Max Scene File

3D Image Files

MDB file extension

Microsoft Access Database

Database Files

MOBI file extension

Mobipocket eBook

eBook Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

THM file extension

Thumbnail Image File

Raster Image Files

TIF file extension

Tagged Image File

Raster Image Files

VCF file extension

vCard File

Data Files

ZIP file extension

Zipped File

Compressed Files