[scrollaway]

You might be overthinking this. I agree with the philosophy that stricter is better, but in this case what do you expect broken hints to do?

They’re not used for rendering, they’re used for figuring out what to fetch. A HEAD request would be far less efficient than knowing ahead of time what to fetch: 1 request versus 2N+1 requests.

What you suggest sounds all fine but the entire web is user input for a browser, so no matter what, you need to define how to fail. If you can fail gracefully, you might as well do so, because a failure might not even be triggered by bad code/configuration on your side but simply by flaky network issues.

[anyfoo]

Yeah, I get how those hints make sense, now that you (and others in the thread) have told me how things are, and I did overlook that HEAD is still an extra request, while the attributes are (effectively) for free.

I do wish that content negotiation (e.g. Accept headers) worked properly. In the end though, those hints implement a subset of content negotiation in a reasonable way, given the state of affairs.

[vbezhenar]

Just don't ignore filename extension. favicon.svg is SVG and that's about it. If you don't support SVG, don't download it. If you want to store png in favicon.svg, don't do that.

[account42]

The web runs on mime types and file extensions are irrelevant except for buggy browsers that try to be too clever (Internet Explorer).