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

APP file extension

Mac OS X Application

Executable Files

DEB file extension

Debian Software Package

Compressed Files

DRV file extension

Device Driver

System Files

FNT file extension

Windows Font File

Font Files

ICO file extension

Icon File

System Files

JAR file extension

Java Archive File

Executable Files

JSP file extension

Java Server Page

Web Files

MID file extension

MIDI File

Audio Files

MPG file extension

MPEG Video File

Video Files

PHP file extension

PHP Source Code File

Web Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

THM file extension

Thumbnail Image File

Raster Image Files

TTF file extension

TrueType Font

Font Files

VCD file extension

Virtual CD

Disk Image Files

3DM file extension

Rhino 3D Model

3D Image Files