Add a web console warning when discovering a cross-origin prefetch resource if HTTP cache partitioning is turned on
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(Core :: DOM: Core & HTML, task)
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(Reporter: ehsan.akhgari, Unassigned)
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(Keywords: dev-doc-needed, site-compat)
With HTTP cache partitioning, prefetching cross-origin resources isn't very useful, so we should probably add a web console warning.
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Comment 1•5 years ago
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See also the discussion at https://github.com/w3c/resource-hints/issues/82. It's not entirely clear to me if this feature still has a use in this brave new privacy-first world. (That is, how often is it used for same-origin navigations?)
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Comment 2•5 years ago
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Yeah that's a good point.
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Updated•5 years ago
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Comment 3•3 years ago
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Tim, is this something you can look into?
I guess there are two questions here, is the prefetch code actually taking into account the partitioned principal and could we add a warning? We might even want to consider removing support for cross-origin resources altogether as it'll just waste bandwidth.
I somehow thought we had dropped support or never supported this, but that doesn't seem to be the case.
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Comment 4•3 years ago
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(In reply to Anne (:annevk) from comment #3)
Tim, is this something you can look into?
I guess there are two questions here, is the prefetch code actually taking into account the partitioned principal and could we add a warning? We might even want to consider removing support for cross-origin resources altogether as it'll just waste bandwidth.
Yeah, I can look into this issue.
We have partitioned the prefetch in Bug 1646136. but I am not sure if it's possible to add a warning for this. Will dig into that.
I somehow thought we had dropped support or never supported this, but that doesn't seem to be the case.
I have a question about removing the prefetch for cross-origin resources. Isn't the prefetch still provide benefits for third-party resources? The third-party resources could still be prefetched and put into the partitioned cache. And the cache can still be used for getting the third-party resource later, right?
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Comment 5•3 years ago
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Yeah, I suppose that's right. I had forgotten it also works for subresources that are used by the document being navigated to next. (There's not really a proper specification for this feature unfortunately.) But that would only work if that document has the same partition.
I'm not sure then if we want a warning here as it might just become noise.
If anything we probably want to have telemetry on how often this is used successfully, but that does not seem like a priority.
I guess from my point of view we can wait a bit here and see what kind of feedback we get, but happy to hear more thoughts.
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Updated•2 years ago
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