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

PDF file extension

Portable Document Format File

Layout Files

GADGET file extension

Windows Gadget

Executable Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

FNT file extension

Windows Font File

Font Files

MPA file extension

MPEG-2 Audio File

Audio Files

7Z file extension

7-Zip Compressed File

Compressed Files

NES file extension

Nintendo (NES) ROM File

Game Files

HTML file extension

Hypertext Markup Language File

Web Files

THM file extension

Thumbnail Image File

Raster Image Files

SAV file extension

Saved Game

Game Files

XML file extension

XML File

Data Files

RTF file extension

Rich Text Format File

Text Files

DLL file extension

Dynamic Link Library

System Files

CSS file extension

Cascading Style Sheet

Web Files

SLN file extension

Visual Studio Solution File

Developer Files