That's an existing Firefox feature called First Party Isolation. Here's a plugin that toggles it: https://github.com/mozfreddyb/webext-firstpartyisolation http

That's an existing Firefox feature called First Party Isolation. Here's a plugin that toggles it: https://github.com/mozfreddyb/webext-firstpartyisolation https://github.com/mozfreddyb/webext-firstpartyisolation It sometimes (rarely) breaks payment processors but otherwise works fine