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

NES file extension

Nintendo (NES) ROM File

Game Files

SDF file extension

Standard Data File

Data Files

7Z file extension

7-Zip Compressed File

Compressed Files

M4A file extension

MPEG-4 Audio File

Audio Files

SWF file extension

Shockwave Flash Movie

Video Files

PART file extension

Partially Downloaded File

Misc Files

TIFF file extension

Tagged Image File Format

Raster Image Files

PDB file extension

Program Database

Database Files

ODT file extension

OpenDocument Text Document

Text Files

TOAST file extension

Toast Disc Image

Disk Image Files

YUV file extension

YUV Encoded Image File

Raster Image Files

UUE file extension

Uuencoded File

Encoded Files

JS file extension

JavaScript File

Web Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

ICNS file extension

Mac OS X Icon Resource File

System Files