Event: timeStamp property

Available in workers

The timeStamp read-only property of the Event interface returns the time (in milliseconds) at which the event was created.

Value

This value is the number of milliseconds elapsed from the beginning of the time origin until the event was created. If the global object is Window, the time origin is the moment the user clicked on the link, or the script that initiated the loading of the document. In a worker, the time origin is the moment of creation of the worker.

The value is a DOMHighResTimeStamp accurate to 5 microseconds (0.005 ms), but the precision is reduced to prevent fingerprinting.

Example

HTML

<p>
  Focus this iframe and press any key to get the current timestamp for the
  keypress event.
</p>
<p>timeStamp: <span id="time">-</span></p>

JavaScript

function getTime(event) {
  const time = document.getElementById("time");
  time.firstChild.nodeValue = event.timeStamp;
}
document.body.addEventListener("keypress", getTime);

Result

Reduced time precision

To offer protection against timing attacks and fingerprinting, the precision of event.timeStamp might get rounded depending on browser settings. In Firefox, the privacy.reduceTimerPrecision preference is enabled by default and defaults to 2ms. You can also enable privacy.resistFingerprinting, in which case the precision will be 100ms or the value of privacy.resistFingerprinting.reduceTimerPrecision.microseconds, whichever is larger.

For example, with reduced time precision, the result of event.timeStamp will always be a multiple of 2, or a multiple of 100 (or privacy.resistFingerprinting.reduceTimerPrecision.microseconds) with privacy.resistFingerprinting enabled.

// reduced time precision (2ms) in Firefox 60
event.timeStamp;
// Might be:
// 9934
// 10362
// 11670
// …

// reduced time precision with `privacy.resistFingerprinting` enabled
event.timeStamp;
// Might be:
// 53500
// 58900
// 64400
// …

Specifications

Browser compatibility