We tried a few times. We got as far as gating the ability to push into the "real history stack" [1] behind a user activation (e.g. click). But, it's easy to get the user to click somewhere: just throw up a cookie banner or an "expand to see full article" or similar.

We weren't really able to figure out any technical solution beyond this. It would rely on some sort of classification of clicks as leading to "real" same-document navigations or not.

This can be done reasonably well as long as you're in a cooperative relationship with the website. For example, if you're trying to classify whether a click should emit single-page navigation performance entries for web performance measurement. (See [2].) In such a case, if the browser can get to (say) 99% accuracy by default with good heuristics and provide site owners with guidance on how to annotate or tweak their code for the remaining 1%, you're in good shape.

But if you're in an adversarial relationship with the website, i.e. it's some malicious spammer trying to hijack the back button, then the malicious site will just always go down the 1% path that slips through the browser's heuristics. And you can try playing whack-a-mole with certain code patterns, but it just never ends, and isn't a great use of engineering resources, and is likely to start degrading the experience of well-behaved sites by accident.

So, policy-based solutions make sense to me here.

[1]: "real history stack": by this I mean the user-visible one that is traversed by the browser's back button UI. This is distinct from the programmer-visible one in `navigation.entries()`, traversed by `navigation.back()` or `history.back()`. The browser's back button is explicitly allowed to skip over programmer-visible entries. https://html.spec.whatwg.org/multipage/speculative-loading.h...

[2]: https://developer.chrome.com/docs/web-platform/soft-navigati...

> We tried a few times

Classify history API, canvas etc etc as "webapp" APIs, and have them show a similar dialog to the webcam dialog.

Then I can just click no, and the scripts on the page can't mess around.

Yes Google Maps is great. No, my favorite news site doesn't need that level of access to my browser or machine, it just needs to show some images and text.

The back button itself feels overloaded. There's "go to previous state" and then there's "go to previous origin." In an ideal world when I doubleclick on the back button what I mean is: "get me off of this site, now."