"prefetch" not allowed in "<a>"?

[mgeier]

This has been added in #2168.

I'm really not an expert in this, but I've been reading https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Attributes/rel, which mentions that prefetch is Not allowed in anything except <link>.

The same page says about rel="next":

When included in a <link>, browsers may assume that document will be fetched next, and treat it as a resource hint.

So I guess it would be good to add <link rel="next" ...>, or maybe <link rel="next prefetch" ...>, but I'm not sure whether latter makes a difference.

[ehuss]

Yea, from what I'm reading, it is only valid for a <link> tag (same with https://html.spec.whatwg.org/multipage/links.html#link-type-prefetch).

I wonder if it is even worth having at all? I'm not finding any other sites or tools that do anything similar.

[mgeier]

I don't know whether it's worth having, but I found another interesting piece of information in the page you linked (https://html.spec.whatwg.org/multipage/links.html#link-type-next):

When the next keyword is used with a link element, user agents should process such links as if they were using one of the dns-prefetch, preconnect, or prefetch keywords. Which keyword the user agent wishes to use is implementation-dependent; for example, a user agent may wish to use the less-costly preconnect processing model when trying to conserve data, battery power, or processing power, or may wish to pick a keyword depending on heuristic analysis of past user behavior in similar scenarios.

I don't know about browser support or any practical relevance, but according to the standard text, I think <link rel="next" ...> would be the right thing to do.

Maybe @pickfire (who added prefetch in #2168) has an opinion?

I'm not finding any other sites or tools that do anything similar.

Sphinx does it, see e.g. https://www.sphinx-doc.org/en/master/usage/quickstart.html

And LaTeX2HTML seems to do it as well, see e.g. https://ccrma.stanford.edu/~jos/resample/Theory_Ideal_Bandlimited_Interpolation.html