Re: Using preload for "async" CSS by changing `rel` trick

On Sat, Jan 13, 2018 at 7:39 AM, Ilya Grigorik <> wrote:
> On Fri, Jan 12, 2018 at 10:24 PM, Ben Maurer <> wrote:
>>>> We use the fact that a resource has been downloaded to reveal content
>>>> that depends on the JS/CSS that we are fetching. So if rel=preload told use
>>>> a.css is available we'll insert HTML that uses a.css into the DOM. Even a
>>>> single frame of the browser doing something like parsing the file would
>>>> create a disruptive user experience.
>>> Right, I see. I think that's a great use case to raise against HTML spec
>>> and see what the guidance is there — this is not preload specific, same
>>> applies for resources coming from HTTP cache, serviceworker, etc.
>> Is the correct formulation of the question "does the presence of a
>> resource in the fetch group's response cache [which is what the preload spec
>> says it adds the stylesheet to] guarantee that inserting a <link> with an
>> href to that resource will synchronously apply to the DOM"
> I'll defer to Anne on this one. :-)

Well, you shouldn't, since this is the complaint I've been making to
you for a number of years now about the state of these features. You
haven't defined them end-to-end, so the answer to these questions
remains unclear. Having said that, I don't think we'd want to give
synchronous guarantees, and especially not that the resource is
already parsed as CSS and has the relevant data structures created.


Received on Saturday, 13 January 2018 07:44:19 UTC