Cadence distribution analyzer

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Average frame time per second
Interval distribution

Live test results

Median cadence— ms
Cadence jitter— ms
Interval spread— ms
Variation— %
Within ±10% band— %
Alternation signal—
Consistency score— / 100
Irregular intervals— events

Use the timeline and distribution together: a narrow cluster normally indicates more even delivery.

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Cadence pattern analysis

Frame Pacing Test

The frame pacing test focuses on distribution and rhythm: how closely intervals cluster, whether patterns alternate, and whether slow events recur. Timeline and histogram views complement the summary metrics.

What Is Frame Pacing?

Frame pacing describes the spacing of delivered frames over time. A sequence can have the desired average FPS yet poor pacing if intervals alternate between short and long values. Even pacing forms a narrow interval distribution and a comparatively flat timeline. Uneven frame pacing creates a wider distribution, repeated peaks, or visible bands that can make motion feel less steady.

This browser frame pacing test records requestAnimationFrame() intervals. It reports median cadence, median absolute jitter, interval spread, coefficient of variation, consistency score, and irregular interval count. Its histogram shows where intervals cluster, while the time series preserves their order. Those two views make it distinct from a frame-time page centered primarily on tail latency and budgets.

Frame Pacing vs Frame Time

Frame time is one interval; frame pacing is the pattern formed by many intervals. A frame-time analysis often asks how long the P99 or worst frame took. A pacing analysis asks whether frames arrived at regular spacing and whether the distribution has multiple modes. The same raw timestamps support both views, but the interpretive questions differ.

For example, intervals alternating between roughly 8 and 25 ms can average near a familiar rate, yet the rhythm is not equivalent to a sequence consistently near 16.67 ms. The timeline exposes alternation; the histogram may show two clusters. The consistency score then provides a compact relative-jitter summary, without rewarding higher absolute FPS.

How to Get Started

Run the tool with the browser window fully on the active display and no deliberate tab switching. Thirty seconds is a useful initial duration. During the test, glance at the timeline for recurring structure, then use the histogram after enough samples have formed. A small sample can look artificially tidy or fragmented.

  1. Start with a quiet baseline and wait through the 1.2-second warm-up.
  2. Compare histogram width, median cadence, variation, and repeated timeline shapes.
  3. Repeat with one changed condition; consistent differences across runs matter more than a one-point score change.

Why Even Frame Delivery Matters

Motion is sampled in time. When update intervals are even, an object moving at constant speed advances in predictable visual steps. When delivery bunches and pauses, those steps vary, and the eye may perceive judder even if total frames over a second remain similar. Consistent feedback can also make an interactive interface feel more predictable.

Frame pacing is not the only contributor to motion quality. Display persistence, pixel response, refresh behavior, synchronization, motion speed, and content all matter. The frame pacing test isolates browser callback rhythm. Pair it with the motion blur and tearing inspection tools when the concern is visual presentation rather than scheduling alone.

Signs of Poor Frame Pacing

Look for a broad histogram, two or more distinct peaks, a sawtooth timeline, periodic long intervals, elevated coefficient of variation, or repeated spike events. One extreme maximum may be an interruption rather than a pacing pattern. Recurrence is the key: a shape that repeats every few frames or reappears in several controlled runs deserves more attention.

The ±10 percent band reports how many intervals remain close to the median cadence. The alternation signal ignores tiny deviations, then looks for meaningful intervals switching between above and below the median. A possible or strong pattern is a prompt to inspect the timeline, not a fault verdict. At some refresh rates, interval quantization can create neighboring clusters even when motion looks acceptable, so repeat surprising patterns in another current browser.

Common Uses for a Frame Pacing Test

Web developers can compare animation implementations, identify periodic work, or verify that an optimization narrows the cadence distribution. Display users can observe how browser cadence changes after switching refresh settings or monitors. Learners can see why two sessions with similar average FPS may not look alike. Controlled screen recordings can help document a pattern, although recording itself may affect performance.

For native games, use frame-time capture from the game or a presentation analysis tool. A browser pacing result does not transfer directly because the workload, rendering API, synchronization, and frame queue differ. The conceptual reading—narrow intervals are more even—still helps when interpreting proper game telemetry.

Limitations and Careful Interpretation

The test observes scheduled browser callbacks rather than certified display presentation. Browser policies, operating-system load, extensions, battery saver, multiple monitors, remote sessions, and variable refresh behavior can alter intervals. Hidden-tab gaps are excluded, and invalid values are filtered, but no browser test can isolate every layer in the rendering chain.

The consistency score is a site-specific summary documented in the methodology, not an industry grade. An even lower rate may score highly because pacing and speed are intentionally separated. Use the histogram, timeline, and raw interval summaries together. The tool cannot automatically prove a monitor, GPU, or browser is defective or guarantee smooth behavior in another application.