I think the OP (hat off!) needed a way to transfer data to the front-end of another application. Since there's no back end involved, the only available channel is the request URL
Not quite. I have a system that uses a custom userscript to create an extra button on certain webpages that, when clicked, scrapes some data from the current page and copies a lightly encoded version to the user's clipboard. They then switch to another webpage and paste it in a box.
I've also gotten data from place to place using scraping from temporary iframes (same site).