In Fixing the URL params performance penalty , Barry Pollard sets up a very clear real-world conundrum. The content at these two URLs is probably the same:

https://www.example.com/

https://www.example.com/?utm_source=email

The content at these two URLs is probably not:

https://www.example.com/products?productid=1234

https://www.example.com/products?productid=5678

Who cares? Cache cares. Because content with different query params might be different, the various tech that deals with caching has to assume it will be different. But that sucks tho. And it’s not a new problem.

I’m not sure what the history or landscape of solutions is for this, but one from the Chrome gang that is rolling out from them is a new header: No-Vary-Search .…