Windows File Types

What file types accomplish in Microsoft Windows

In Microsoft Windows, file types are the types of files that Windows has a program to act upon. This may be a standard Windows program like Notepad or something that was installed after you bought your computer, like Adobe Photoshop. It could have been installed from a CD or downloaded from the Internet.

For more information see our Computer Help on Downloads and Free Software.

file types are the three letters that appear after the dot . in a file name.

For example HiMom.txt is a Text file produced by Windows Notepad where the file name is HiMom and the file type is .txt.

You may or may not see the file type depending on how your Folder Options are set. For more information on changing your Folder Options settings go here

Some file types are Windows system files. These are, in alphabetical order:

None of the above should ever be deleted. It could affect how Windows operates.

In addition to System Files, there are many common file types that you may find on your computer like:

A complete list of file types may be found on Wikipedia here.


To determine if a program that will open a specific file type is on your computer or not, go to Windows Explorer or your C:/ drive. Left click on Folder Options... and click on the File Types tab.

Folder Options


Unassigned File Types



This takes you to all the File Types on your system.







the first ones, starting with [NONE] are the file types that Windows knows about but there are numerous programs that could operate on the data and none are on your computer.


Now scroll down past all the [NONE] entries until you get to some with a file type association.










Assigned File Types





These are the files for which you have the appropriate program installed to operate or display the data.


In this example we have scrolled down to the J's and because Irfanview is on our system with All Graphics File Types selected the graphics file types starting with J are assigned to Irfanview. .JPX is assigned to Corel Paint Shop Pro.


Don't try changing any of the file extensions unless you are a computer expert. You can easily cripple your computer or even prevent it from starting properly.


Only look at the File Types to see if you have the program installed to open a file. The extensions are set during a program install process and should never be set by a user unless you know what you are doing.






Now you know about File Types. Use the knowledge wisely.