I'll do that once any of the top 4 AI chatbots says they'll start making requests with this header. Before that it's just a neat idea with no adoption.
I also think it's exceedingly unlikely that any of the top 4 chatbots would choose to load websites this way. Too many risks for a 0.01% adoption even years later.
You can see current support here:
https://acceptmarkdown.com/status
Claude Code’s been doing this for at least a year already and I assume Claude Cowork does it too as a result. That’s already millions of users, so it’s not “just a neat idea with no adoption”.
Anthropic's own documentation site also returns markdown (of sorts) if you append ".md", and Claude Code knows it.
E.g.: https://code.claude.com/docs/en/overview.md
I mean, it's exceptionally easy for them to add it. Even with low adoption. Somewhere in the bowels of chatgpt there is code that queries for html, and then parses that to markdown or something similar. All this would be is adding the logic to request markdown if available, then bypass the html->markdown step if you get markdown back.
Also it's not that hard at crawl time to transform HTML into markdown before passing to the LLM.