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

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-clients 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.