Router Timing Dashboard

about the new fields

• workerMatchedRouterSource — the source declared by the matched Static Router rule: "cache", "network", "fetch-event", "race-network-and-fetch-handler", or "" (no rule matched)
• workerFinalRouterSource — what actually delivered the bytes. May differ from the matched source if the primary source was unavailable (e.g. cache miss → network fallthrough)
• Both fields are empty strings when no service worker handled the request

code

// Observe all resource timings on the page
performance.getEntriesByType('resource').forEach(entry => {
  // Chrome 151: new fields
  const matched = entry.workerMatchedRouterSource; // "" if no SW rule
  const final   = entry.workerFinalRouterSource;   // "" if no SW

  console.log({
    url: entry.name,
    matched,  // which Static Router rule source was selected
    final,    // what actually served the response
    duration: entry.duration.toFixed(1) + 'ms',
  });
});

// Use PerformanceObserver to capture in real time
const obs = new PerformanceObserver(list => {
  for (const entry of list.getEntries()) {
    if (entry.workerMatchedRouterSource) {
      console.log('SW router hit:', entry.workerMatchedRouterSource);
    }
  }
});
obs.observe({ type: 'resource', buffered: true });

see also

• Timing Field Inspector
• Router Source Values Explorer
• ChromeStatus entry
• Resource Timing Level 2 spec