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

PHP file extension

PHP Source Code File

Web Files

CPL file extension

Windows Control Panel Item

System Files

PRF file extension

Outlook Profile File

Settings Files

DDS file extension

DirectDraw Surface

Raster Image Files

EPUB file extension

Open eBook File

eBook Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

EPS file extension

Encapsulated PostScript File

Vector Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

C file extension

C/C++ Source Code File

Developer Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

3DM file extension

Rhino 3D Model

3D Image Files

M4A file extension

MPEG-4 Audio File

Audio Files

JAVA file extension

Java Source Code File

Developer Files

THM file extension

Thumbnail Image File

Raster Image Files

DMG file extension

Mac OS X Disk Image

Disk Image Files