PerformanceLongAnimationFrameTiming

Description

Long animation frames (LoAFs) are rendering updates that are delayed beyond 50ms. LoAFs can result in slow user interface (UI) updates, making controls appear unresponsive and causing janky (non-smooth) animated effects and scrolling. This often leads to user frustration.

The PerformanceLongAnimationFrameTiming interface provides the following granular set of information on LoAFs, allowing developers to narrow down their root causes:

• A detailed set of timestamps for each LoAF.
• Detailed information on each script that contributed to creating the LoAF, via the PerformanceLongAnimationFrameTiming.scripts property. This returns an array of PerformanceScriptTiming objects, one for each script.

PerformanceLongAnimationFrameTiming inherits from PerformanceEntry.

Instance properties

This interface directly defines the following properties:

PerformanceLongAnimationFrameTiming.blockingDuration Read only

Returns a DOMHighResTimeStamp indicating the total time in milliseconds that the main thread was blocked from responding to high priority tasks, such as user input. This is calculated by taking all the long tasks within the LoAF that have a duration of more than 50ms, subtracting 50ms from each, adding the rendering time to the longest task time, and summing the results.

PerformanceLongAnimationFrameTiming.firstUIEventTimestamp Read only

Returns a DOMHighResTimeStamp indicating the time of the first UI event — such as a mouse or keyboard event — to be queued during the current animation frame.

PerformanceLongAnimationFrameTiming.paintTime

Returns the timestamp when the rendering phase ended and the animation frame started.

PerformanceLongAnimationFrameTiming.presentationTime

Returns the timestamp when the UI update was actually drawn on the screen.

PerformanceLongAnimationFrameTiming.renderStart Read only

Returns a DOMHighResTimeStamp indicating the start time of the rendering cycle, which includes Window.requestAnimationFrame() callbacks, style and layout calculation, ResizeObserver callbacks, and IntersectionObserver callbacks.

PerformanceLongAnimationFrameTiming.scripts Read only

Returns an array of PerformanceScriptTiming instances.

PerformanceLongAnimationFrameTiming.styleAndLayoutStart Read only

Returns a DOMHighResTimeStamp indicating the beginning of the time period spent in style and layout calculations for the current animation frame.

It also extends the following PerformanceEntry properties, qualifying and constraining them as described:

PerformanceEntry.duration Read only

Returns a DOMHighResTimeStamp representing the time taken in milliseconds to process the LoAF in its entirety.

PerformanceEntry.entryType Read only

Returns the entry type, which is always "long-animation-frame".

PerformanceEntry.name Read only

Returns the entry name, which is always "long-animation-frame".

PerformanceEntry.startTime Read only

Returns a DOMHighResTimeStamp representing the time when the animation frame started.

Instance methods

PerformanceLongAnimationFrameTiming.toJSON()

Returns a JSON representation of the PerformanceLongAnimationFrameTiming object.

Examples

See Long animation frame timing for examples related to the Long Animation Frames API.

Specifications

Browser compatibility

See also

• Long animation frame timing
• PerformanceScriptTiming