Because GM.getValue/GM.setValue don't seem to work uniformly with all userscript mangaers, I'm attempting to utilize "web-messaging", for storing values, as a general replacement to GM.getValue/GM.setValue.

This is my most recent attempt: https://openuserjs.org/scripts/sjehuda/Dimmer_(web-messaging)

The problem is that upon reload, the value is erased, thus window.addEventListener('message', receiver); returns undefined.

This script works and uses localStorage.

Is it wise to use localStorage over GM.getValue/GM.setValue?

I guess a given website can read the localStorage value set by a userscript.

Can websites read values of GM.getValue?

@admins Please change title to "Standard alternatives to GM.getValue/GM.setValue".

Thank you