What is the point of "X-" prefixes? To make it clear that the thing in question is implementation specific and should not be relied on if you want it to work on

What is the point of "X-" prefixes? To make it clear that the thing in question is implementation specific and should not be relied on if you want it to work on all implementations. Should "X-" things be created? Yes. If the people creating new implementations can't be bothered to make their changes official, or what those things does changes, then they use "X-". You should assume "X-" means "don't use this". Why do the "X-" things persist and get implemented by everyone eventually? Because bureaucracy and standards groups suck and don't keep up with the times. What does a standard group saying "don't use X-" mean? It is just a lame attempt by the group to stop people from doing things they aren't informed of or in charge of. Guess what IETF: The people who care that you said this don't create "X-" things for the most part. The people who do are just going to ignore this.