[grose]

Here's an official Google page telling you to sniff UAs or their new feature will break everything: https://www.chromium.org/updates/same-site/incompatible-clie...

Edit: OK, this isn't progressive enhancement. But it's still a major problem you have to sniff the User-Agent for. I don't want to sniff UAs either but when Chrome is wont to change how fundamental parts of the web work like cookies it's sometimes necessary. I know UA hints will still allow you to do this, but requiring a second request is going to make things like redirect pages difficult to implement.

[minitech]

SameSite=None isn’t progressive enhancement.

[grose]

You're right, I should have replied elsewhere. By the way, if anyone knows what this _is_ called I would be interested to know. As far as I can see it's basically feature detection with no other way of detecting it besides the UA.