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PerformanceNavigationTiming: activationStart property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

Non-standard: This feature is not standardized. We do not recommend using non-standard features in production, as they have limited browser support, and may change or be removed. However, they can be a suitable alternative in specific cases where no standard option exists.

The activationStart read-only property represents the time between when a document starts prerendering and when it is activated.

Value

A DOMHighResTimeStamp representing the duration between document prerendering start and activation in milliseconds.

The value is 0 if the page has not prerendered or is still prerendering.

Examples

Detecting prerendered pages

When a prerendered document is activated, activationStart is set to the current time. The following function can check whether a page is prerendering or has already prerendered:

function pagePrerendered() {
  return (
    document.prerendering ||
    self.performance?.getEntriesByType?.("navigation")[0]?.activationStart > 0
  );
}

Measuring user-perceived performance milestones

With prerendered pages, a page may have been created long before it was actually navigated to. When using the Performance API on prerendered pages, it is vital to compare returned values with activationStart in order to avoid misleading measurements.

// Time to when activation occurred
let activationStart =
  performance.getEntriesByType("navigation")[0].activationStart;

// Time to first paint
let firstPaint = performance.getEntriesByName("first-paint")[0].startTime;

// Time to first contentful paint
let firstContentfulPaint = performance.getEntriesByName(
  "first-contentful-paint",
)[0].startTime;

console.log(`time to first paint: ${firstPaint - activationStart}`);
console.log(
  `time to first-contentful-paint: ${firstContentfulPaint - activationStart}`,
);

Specifications

This feature does not appear to be defined in any specification.>

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	WebView on iOS
`activationStart`	108	108	No	94	No	57	No	43	No	7.0	57	No