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

AVI file extension

Audio Video Interleave File
Video Files

CFM file extension

ColdFusion Markup File
Web Files

CGI file extension

Common Gateway Interface Script
Executable Files

CSR file extension

Certificate Signing Request File
Web Files

GED file extension

GEDCOM Genealogy Data File
Data Files

IBOOKS file extension

Multi-Touch iBook
Data Files

KMZ file extension

Google Earth Placemark File
GIS Files

M3U file extension

Media Playlist File
Audio Files

MOBI file extension

Mobipocket eBook
eBook Files

OBJ file extension

Wavefront 3D Object File
3D Image Files

PART file extension

Partially Downloaded File
Misc Files

PDF file extension

Portable Document Format File
Layout Files

TAX2012 file extension

TurboTax 2012 Tax Return
Data Files

VCF file extension

vCard File
Data Files

YUV file extension

YUV Encoded Image File
Raster Image Files