demo · v133

firstResponseHeadersStart

Fetch a URL and read the PerformanceResourceTiming entry. The page shows both the restored responseStart definition and the new firstResponseHeadersStart milestone side by side.

milestonevalue (ms)

checking support...

the code

const entry = performance.getEntriesByType("resource").slice(-1)[0];
console.log({
  fetchStart: entry.fetchStart,
  firstResponseHeadersStart: entry.firstResponseHeadersStart, // NEW
  responseStart: entry.responseStart,
  responseEnd: entry.responseEnd,
});

see also