@VisualStuart Not just YouTube! That ? in a URL almost universally means “the rest of this is not essential”. You may need it for, say, keeping your browser aware that your shopping cart has 4 items in it, or for TicketBastard to know you are 8,762nd in the queue, but if you are sending a link to a friend as a gift idea in the middle of browsing? They don’t need any of that stuff. The ? signals the start of the spyware, on YT, Amazon, EBay, most e-commerce sites, you name it.
@dwenius This is perhaps a *little* overstated. I'm a retired software architect here, so believe me there are many good and unharmful uses for query strings, so let's not go overboard. But you're quite right that in many cases they are not absolutely necessary for a given site or page.
To test what is needed and what is not, I will often paste a URL into the Address bar of the browser, try removing a chunk of a suspicious query string, hit Enter and see if it takes me where I want to be.