Calculated over a 60-frame moving window using native requestAnimationFrame timestamps.
Smooth, stutter-free movement confirms active hardware acceleration and stable VSync frame delivery.
Test your monitor's physical refresh rate in Hertz (Hz) directly in your browser with BunchTool's free Screen Refresh Rate Checker. By capturing high-resolution timestamps across 60 consecutive requestAnimationFrame rendering cycles, this tool calculates your exact display refresh frequency — distinguishing 60Hz, 120Hz, 144Hz, 240Hz, and variable refresh rate (VRR) setups with 100% private, client-side browser execution.
requestAnimationFrame timestamp deltasKeep this tab active and visible. Browsers throttle requestAnimationFrame callbacks to 1Hz on hidden or unfocused tabs to save energy.
Watch the real-time Hertz counter calculate your monitor's exact refresh frequency over a rolling 60-frame window.
Check the bouncing ball animation to verify smooth, stutter-free movement, confirming active browser hardware acceleration and stable VSync delivery.
Uses DOMHighResTimeStamp values from requestAnimationFrame callbacks. Computing moving averages across 60 frames eliminates transient OS micro-stutters for exact Hz accuracy.
Detects and classifies standard gaming and productivity display rates out of the box — 30Hz, 60Hz, 120Hz, 144Hz, and 240Hz — as well as variable refresh rate (G-Sync / FreeSync) setups.
All timing calculations run locally in browser JavaScript. Display specifications are never recorded, logged, or transmitted to any external server.
requestAnimationFrame API, which synchronizes callback execution with the display's vertical refresh cycle (VSync). By recording high-resolution DOMHighResTimeStamp values across 60 frames and computing the average inter-frame delta, Hz is calculated as 1000 / avgDelta.requestAnimationFrame timing may cap at 60 FPS or exhibit frame pacing jitter even if your physical display is configured for 120Hz or higher.requestAnimationFrame loops at the current active VSync lock rate of your desktop, showing your current desktop refresh frequency accurately.Screen Refresh Rate (Hertz): Measured in Hertz (Hz), refresh rate indicates how many times per second a monitor redraws the screen image. A standard 60Hz display refreshes every 16.67 milliseconds, a 120Hz display every 8.33ms, a 144Hz display every 6.94ms, and a 240Hz display every 4.17ms. Higher refresh rates dramatically reduce motion blur and input latency in fast-paced gaming and desktop navigation.
requestAnimationFrame & VSync: The HTML5 window.requestAnimationFrame() API signals the browser to perform an animation update before the next repaint. Modern browsers align these callbacks directly with the GPU's vertical synchronization (VSync) signal. By tracking consecutive timestamp deltas (timestamp_N - timestamp_N-1), web applications can measure display hardware refresh rates with sub-millisecond precision.
Common high-refresh rate bottlenecks: If a high-refresh monitor (e.g. 144Hz or 240Hz) tests at 60Hz, common culprits include: (1) Windows/macOS display settings defaulting to 60Hz, (2) using an older HDMI 1.4 cable limited to 60Hz at 1440p/4K, (3) browser flags disabling hardware acceleration, or (4) multi-monitor setups where a secondary 60Hz display forces window compositor throttling.