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

FON file extension

Generic Font File

Font Files

3DS file extension

3D Studio Scene

3D Image Files

PHP file extension

PHP Source Code File

Web Files

TOAST file extension

Toast Disc Image

Disk Image Files

CLASS file extension

Java Class File

Developer Files

THM file extension

Thumbnail Image File

Raster Image Files

MSG file extension

Outlook Mail Message

Text Files

WSF file extension

Windows Script File

Executable Files

DB file extension

Database File

Database Files

7Z file extension

7-Zip Compressed File

Compressed Files

JS file extension

JavaScript File

Web Files

DDS file extension

DirectDraw Surface

Raster Image Files

KEY file extension

Keynote Presentation

Data Files

TMP file extension

Temporary File

Backup Files

BMP file extension

Bitmap Image File

Raster Image Files