https://lua-api.factorio.com/latest/index.html says it's "0.18.47" in the top-right corner.
And I don't think it's a caching problem on my side, I have tried all tips shown in https://xkcd.com/1854/ , and I have also tried using a private browsing window.
[1.0.0] Lua API Latest still points to 0.18.47
Re: [1.0.0] Lua API Latest still points to 0.18.47
Fixed, thanks for the report!