PerformanceEventTiming: processingStart property

Baseline 2025

Newly available

Since ⁨December 2025⁩, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

The read-only processingStart property returns the time at which event dispatch started. This is when event handlers are about to be executed.

Value

A DOMHighResTimeStamp timestamp.

Examples

Using the processingStart property

The processingStart property can be used when observing event timing entries (PerformanceEventTiming). For example, to calculate input delay or event processing times.

const observer = new PerformanceObserver((list) => {
  list.getEntries().forEach((entry) => {
    // Full duration
    const duration = entry.duration;
    // Input delay (before processing event)
    const delay = entry.processingStart - entry.startTime;
    // Synchronous event processing time
    // (between start and end dispatch)
    const time = entry.processingEnd - entry.processingStart;
  });
});
// Register the observer for events
observer.observe({ type: "event", buffered: true });