Performance
Baseline Widely available *
This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2015.
* Some parts of this feature may have varying levels of support.
Note: This feature is available in Web Workers.
The Performance interface provides access to performance-related information for the current page.
Performance entries are specific to each execution context. You can access performance information for code running in a window via Window.performance, and for code running in a worker via WorkerGlobalScope.performance.
Instance properties
The Performance interface doesn't inherit any properties.
Performance.eventCountsRead onlyAn
EventCountsmap containing the number of events which have been dispatched per event type.A legacy
PerformanceNavigationobject that provides useful context about the operations included in the times listed intiming, including whether the page was a load or a refresh, how many redirections occurred, and so forth.Performance.timingRead onlyDeprecatedA legacy
PerformanceTimingobject containing latency-related performance information.Performance.memoryRead onlyNon-standardDeprecatedA non-standard extension added in Chrome, this property provides an object with basic memory usage information. You should not use this non-standard API.
Performance.timeOriginRead onlyReturns the high resolution timestamp of the start time of the performance measurement.
Instance methods
The Performance interface doesn't inherit any methods.
Performance.clearMarks()Removes the given mark from the browser's performance entry buffer.
Performance.clearMeasures()Removes the given measure from the browser's performance entry buffer.
Performance.clearResourceTimings()Removes all performance entries with a
entryTypeof"resource"from the browser's performance data buffer.Performance.getEntries()Returns a list of
PerformanceEntryobjects based on the given filter.Performance.getEntriesByName()Returns a list of
PerformanceEntryobjects based on the given name and entry type.Performance.getEntriesByType()Returns a list of
PerformanceEntryobjects of the given entry type.Performance.mark()Creates a
timestampin the browser's performance entry buffer with the given name.Performance.measure()Creates a named
timestampin the browser's performance entry buffer between two specified marks (known as the start mark and end mark, respectively).Performance.measureUserAgentSpecificMemory()ExperimentalEstimates the memory usage of a web application including all its iframes and workers.
Performance.now()Returns a
DOMHighResTimeStamprepresenting the number of milliseconds elapsed since a reference instant.Performance.setResourceTimingBufferSize()Sets the browser's resource timing buffer size to the specified number of
"resource"typePerformanceEntryobjects.Performance.toJSON()Returns a JSON representation of the
Performanceobject.
Events
Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface.
resourcetimingbufferfullFired when the browser's resource timing buffer is full.
