[kijin]

Yeah, it's a neat trick but kinda pointless. In a world with CDNs and HTTP/2, all this does is waste bandwidth in order to look slightly better in artificial benchmarks.

It might improve time to first paint by 10-20ms, but this is a webpage, not a first-person shooter. Besides, subsequent page loads will be slower.

[aitchnyu]

Yup, whereever we deviated from straightforward asset downloads to optimize something, we always end up slower or buggy. Like manually downloading display images or using websockets to upload stuff. Turns out servers and browsers have spent more person-years optimizing it better than me.

[todotask2]

And Critical CSS requires reducing the CSP (Content Security Policy), which I have already hardened almost entirely along with Permissions Policy.

[nashashmi]

Imagine this: before serving the page, a filter seeks out the critical css, inserts it, and removes all css links. Greatly improving page load times and reducing CDN loads.

Edit: on second reading, it seems like you are saying when another page from the same server with the same style loads again, the css would have to be reloaded and This increases bandwidth in cases where a site visitor loads multiple pages. So yes it is optimum for conditions where the referrer is external to the site.