That's the fundamental misunderstanding I was talking about. You don't know what browser is being used. Ever. You only know what the user agent decided to descr

That's the fundamental misunderstanding I was talking about. You don't know what browser is being used. Ever. You only know what the user agent decided to describe itself as and the requests it made to your servers. None of that tells you anything about what happened on the remote computer. Besides, "modern browser" is a complete undefined term that is obviously subject to a lot of interpretation and opinion. Usually this term is used as either a euphemism for "I really want to put spyware on my website" or "I only use badly-designed tools".