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

CRX file extension

Chrome Extension

Plugin Files

EXE file extension

Windows Executable File

Executable Files

APP file extension

Mac OS X Application

Executable Files

NES file extension

Nintendo (NES) ROM File

Game Files

COM file extension

DOS Command File

Executable Files

MAX file extension

3ds Max Scene File

3D Image Files

CAB file extension

Windows Cabinet File

System Files

3DS file extension

3D Studio Scene

3D Image Files

VCD file extension

Virtual CD

Disk Image Files

SRT file extension

SubRip Subtitle File

Video Files

ACCDB file extension

Access 2007 Database File

Database Files

DTD file extension

Document Type Definition File

Developer Files

ICNS file extension

Mac OS X Icon Resource File

System Files

7Z file extension

7-Zip Compressed File

Compressed Files

RTF file extension

Rich Text Format File

Text Files