The PerformanceObserver() constructor creates a new PerformanceObserver object with the given observer callback. The observer callback is invoked when performance entry events are recorded for the entry types that have been registered, via the observe() method.


var observer = new PerformanceObserver(callback);


A PerformanceObserverCallback callback that will be invoked when observed performance events are recorded. When the callback is invoked, its first parameter is a list of performance observer entries and the second parameter is the observer object.

Return value

A new PerformanceObserver object which will call the specified callback when observed performance events occur.


var observer = new PerformanceObserver(function(list, obj) {
  var entries = list.getEntries();
  for (var i=0; i < entries.length; i++) {
    // Process "mark" and "frame" events
observer.observe({entryTypes: ["mark", "frame"]});

function perf_observer(list, observer) {
  // Process the "measure" event 
var observer2 = new PerformanceObserver(perf_observer);
observer2.observe({entryTypes: ["measure"]});


Specification Status Comment
Performance Timeline Level 2
The definition of 'PerformanceObserver()' in that specification.
Candidate Recommendation Initial definition of PerformanceObserver() constructor.

Browser compatibility

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ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
PerformanceObserver() constructorChrome Full support 52Edge Full support ≤79Firefox Full support 57IE No support NoOpera Full support 39Safari Full support 11WebView Android Full support 52Chrome Android Full support 52Firefox Android Full support 57Opera Android Full support 41Safari iOS Full support 11Samsung Internet Android Full support 6.0


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