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

DLL file extension

Dynamic Link Library

System Files

CPL file extension

Windows Control Panel Item

System Files

MP3 file extension

MP3 Audio File

Audio Files

ASPX file extension

Active Server Page Extended File

Web Files

7Z file extension

7-Zip Compressed File

Compressed Files

TIF file extension

Tagged Image File

Raster Image Files

SITX file extension

StuffIt X Archive

Compressed Files

MDF file extension

Media Disc Image File

Disk Image Files

PPS file extension

PowerPoint Slide Show

Data Files

TGA file extension

Targa Graphic

Raster Image Files

JS file extension

JavaScript File

Web Files

PHP file extension

PHP Source Code File

Web Files

AVI file extension

Audio Video Interleave File

Video Files

SRT file extension

SubRip Subtitle File

Video Files

OBJ file extension

Wavefront 3D Object File

3D Image Files