Default apps by file type

Hi, first, what do you see if you go to Settings here?


You should have a list of registered file types- in your case, expect them to be limited to the defaults that are available when you install Windows (+ any others created by programs you may have installed at some point).

You have at least two difficulties.
a. Your portable programs won't be registered to handle any file types.
b. A portable program that handles file types not available on your system can't be assigned to them - as they don't exist.
(Imagine a portable office program - doc and docx don't exists as file types until you install a handler).

If the file type exists, then you may be able to rt click it, Open With and browse to your portable program.
However, as that program is not registered to handle it, I'm not sure quite what you'll end up with (see rtf example below, and consider the effect of assigning an unregistered program to it).

If it doesn't, you will have to create it, and all that goes with it.

You may find this free program helpful:


Also this one (note: I've shown the rtf extension - look at what is needed to handle it- and the program's parameters)

You can see an example of what was needed to support portable browsers here:
Can't define Default APP Windows 10

As you haven't installed programs, you don't have the registry data that defines their relationship with a given file type. A number of things are changed when you assign a program to handle a file type as default, from the necessary command strings to invoke that program, to the icon then assigned to that file type.

For the most part you will be limited to launching a portable program, then browsing to and opening a file.