Performance.now()

« Performance

Summary

The Performance.now() method returns a DOMHighResTimeStamp, measured in milliseconds, accurate to one thousandth of a millisecond equal to the number of milliseconds since the PerformanceTiming.navigationStart property and the call to the method.

Syntax

t = performance.now();

Example

var t0 = performance.now();
doSomething();
var t1 = performance.now();
console.log("Call to doSomething took " + (t1 - t0) + " milliseconds.")

Unlike other timing data available to JavaScript (for example Date.now), the timestamps returned by Performance.now() are not limited to one-millisecond resolution. Instead, they represent times as floating-point numbers with up to microsecond precision.

Also unlike Date.now, the values returned by Performance.now() always increase at a constant rate, independent of the system clock (which might be adjusted manually or skewed by software like NTP).

Specifications

Specification Status Comment
High Resolution Time Recommendation Initial definition

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 20.0 webkit
24.0*
15.0 (15.0) 10.0 15.0 Not supported
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support 4.0 (Yes) 15.0 (15.0) 10.0 Not supported Not supported

NOTE: *Windows version of Chrome 20 through 33, at the time of this writing, returns performance.now() only to millisecond precision.

See also

Document Tags and Contributors

Last updated by: marcwinners,