To reduce security and privacy implications, the HTML and Fetch living standards have some restrictions on when Early Hints can be handled. Chrome ignores Early Hints sent in the following situations to comply these specifications.
Chrome ignores the second and following Early Hints responses. Chrome only handles the first Early Hints response so that Chrome doesn't apply inconsistent security policies (e.g. Content-Security-Policy).
If a resource is preloaded by Early Hints, the corresponding PerformanceResourceTiming object reports
initiatorType is “early-hints”.
performance.getEntriesByName('https://a.test/style.css').initiatorType // => 'early-hints'
Due to an implementation limitation,
initiatorType may not always set to “early-hints”. See the proposal for more details.