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

3DS file extension

3D Studio Scene

3D Image Files

BMP file extension

Bitmap Image File

Raster Image Files

SRT file extension

SubRip Subtitle File

Video Files

CGI file extension

Common Gateway Interface Script

Executable Files

PKG file extension

Mac OS X Installer Package

Compressed Files

CFM file extension

ColdFusion Markup File

Web Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

GED file extension

GEDCOM Genealogy Data File

Data Files

H file extension

C/C++/Objective-C Header File

Developer Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

AI file extension

Adobe Illustrator File

Vector Image Files

SDF file extension

Standard Data File

Data Files

ACCDB file extension

Access 2007 Database File

Database Files

7Z file extension

7-Zip Compressed File

Compressed Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files