I'm trying to open an html page (I get it as a string and parse it) from my fullscreen iOS web application (standalone).
I tried opening a window (window.open) but it doesn't work.
It involves handling a payment method, so I can't redirect back from their page to mine (it's an illegal hack) when I finish.
How can I manage opening the html file in safari and going back?
I don't know of a way that a standalone mode web app can serve up raw HTML to the user without it being hosted somewhere.
If you have a genuine web URL though, you can have the user click a link with
target="_blank"(new tab) and it should open in Safari, instead of the standalone browser. I don't think you can do it via window.open(), because it will be silently blocked as a "pop-up".