Interface PerformanceSnapshot

Current browser performance metrics and retained histories.

interface PerformanceSnapshot {
    cls: number;
    fps: number;
    fpsHistory: number[];
    longAnimationFrames: LongAnimationFrameInfo;
    longTasks: LongTaskInfo;
    memory: MemoryInfo | null;
    memoryHistory: number[];
    memoryMeasurement: MemoryMeasurement | null;
}

Properties

cls: number

Cumulative Layout Shift value collected from layout-shift performance entries.

fps: number

Latest frames-per-second measurement.

fpsHistory: number[]

Recent FPS measurements, capped by maxHistory.

Long animation frames with script attribution, in Chromium browsers that support the Long Animation Frames API. Stays empty elsewhere.

Long task counter and last observed duration.

memory: MemoryInfo | null

Current heap memory information, or null outside browsers that expose performance.memory.

memoryHistory: number[]

Recent memory usage percentages, capped by maxHistory.

memoryMeasurement: MemoryMeasurement | null

Latest page memory measurement, or null before the first one resolves and where performance.measureUserAgentSpecificMemory() is unavailable.