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 inWeb Workers.
ThePerformance 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 viaWindow.performance, and for code running in a worker viaWorkerGlobalScope.performance.
Instance properties
ThePerformance interface doesn't inherit any properties.
Performance.eventCountsRead onlyAn
EventCountsmap containing the number of events which have been dispatched per event type.Performance.navigationRead onlyDeprecatedA 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-standardDeprecatedAnon-standard extension added in Chrome, this property provides an object with basic memory usage information.Youshould not use this non-standard API.
Performance.timeOriginRead onlyReturns the high resolution timestamp of the start time of the performance measurement.
Instance methods
ThePerformance interface doesn't inherit any methods.
Performance.clearMarks()Removes the givenmark from the browser's performance entry buffer.
Performance.clearMeasures()Removes the givenmeasure from the browser's performance entry buffer.
Performance.clearResourceTimings()Removes allperformance entries with an
entryTypeof"resource"from the browser's performance data buffer.Performance.getEntries()Returns a list of
PerformanceEntryobjects based on the givenfilter.Performance.getEntriesByName()Returns a list of
PerformanceEntryobjects based on the givenname andentry type.Performance.getEntriesByType()Returns a list of
PerformanceEntryobjects of the givenentry type.Performance.mark()Creates a
timestampin the browser'sperformance entry buffer with the given name.Performance.measure()Creates a named
timestampin the browser's performance entry buffer between two specified marks (known as thestart mark andend 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 usingaddEventListener() or by assigning an event listener to theoneventname property of this interface.
resourcetimingbufferfullFired when the browser'sresource timing buffer is full.