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

BAK file extension

Backup File

Backup Files

CSR file extension

Certificate Signing Request File

Web Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

EXE file extension

Windows Executable File

Executable Files

GADGET file extension

Windows Gadget

Executable Files

GPX file extension

GPS Exchange File

GIS Files

INDD file extension

Adobe InDesign Document

Layout Files

KEY file extension

Keynote Presentation

Data Files

MP4 file extension

MPEG-4 Video File

Video Files

PDF file extension

Portable Document Format File

Layout Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

RPM file extension

Red Hat Package Manager File

Compressed Files

SH file extension

Bash Shell Script

Developer Files

VB file extension

VBScript File

Executable Files

WSF file extension

Windows Script File

Executable Files