[byuu]

> HTTP/2 is all 100% mandatory

That's a nice idea in theory, but what makes you think anyone is going to adhere to that?

Developers have always, and will always, do whatever they want when they implement your standards.

It was bad enough that when I worked on a binary delta patching format, I made sure there were absolutely zero possible undefined values, because I knew someone might try and use them to add new functionality in.

For something as complex as HTTP, I can guarantee you people will ignore parts of the spec they don't care about. And you can yell at them and say it's not a valid/legal HTTP/2 implementation, but they won't care. They'll keep on doing what they're doing.

[TylerE]

It's still a much better situation than HTTP/1.1. At least an HTTP/2 compliant implementation has an exact definition, that it either is, or isn't. An HTTP/1.1 implementation has a vast number of corner cases and optional bits.

Sure, if you're out-of-spec, all bets are off. It's just that with hTTP/1.1 even 100% in-spec implementations are a pretty wide target zone.