v151 · performance · timing

Navigation Timing Probe

Chrome 151 adds a Timing-Allow-Origin opt-in for navigation redirect chains. When a navigation crosses origins via redirects, the PerformanceNavigationTiming redirect timing fields (redirectStart, redirectEnd) are zeroed unless the destination origin opts in via Timing-Allow-Origin.

Navigation vs. Subresource

The Chrome 151 change is specifically about navigation redirect timing. Previously, PerformanceResourceTiming for subresources (fetch, img, script) had TAO — but PerformanceNavigationTiming redirect fields were always zeroed for cross-origin redirects. This opt-in lets the destination server expose them.

Field	Value	Status

Zeroed fields (0) indicate the timing data is hidden due to cross-origin restrictions. Chrome 151 allows the destination server to expose navigation redirect timing via TAO.

Reading PerformanceNavigationTiming redirect fields

// Read the current page's navigation timing
const navEntries = performance.getEntriesByType("navigation");
for (const entry of navEntries) {
  console.log("redirectStart:", entry.redirectStart);
  console.log("redirectEnd:", entry.redirectEnd);
  // If the page was reached via a cross-origin redirect,
  // these will be 0 unless the server sent:
  //   Timing-Allow-Origin: * (or your origin)
}

Chrome 151 extends the TAO opt-in to PerformanceNavigationTiming redirect chains, so analytics can measure redirect latency for navigations — not just subresources.

references

implementation reference

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