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

CUR file extension

Windows Cursor

System Files

7Z file extension

7-Zip Compressed File

Compressed Files

FNT file extension

Windows Font File

Font Files

MSI file extension

Windows Installer Package

Misc Files

RTF file extension

Rich Text Format File

Text Files

VCXPROJ file extension

Visual C++ Project

Developer Files

MP4 file extension

MPEG-4 Video File

Video Files

MDF file extension

Media Disc Image File

Disk Image Files

CPP file extension

C++ Source Code File

Developer Files

DLL file extension

Dynamic Link Library

System Files

DXF file extension

Drawing Exchange Format File

CAD Files

MAX file extension

3ds Max Scene File

3D Image Files

DOC file extension

Microsoft Word Document

Text Files

BIN file extension

Binary Disc Image

Disk Image Files

PHP file extension

PHP Source Code File

Web Files