Refresh Rate Test — Check Monitor Hz & Frame Rate Online

Understanding Display Refresh Rates: Hz, Timings, and Compositor Sync

The refresh rate of a computer monitor, laptop display, or smartphone screen specifies the number of discrete times per second that the physical display panel scans, refreshes, and redraws its illuminated pixels. Measured in Hertz (Hz), this parameter sets the ultimate upper boundary on how fluidly visual motion can be transmitted to the human retina.

A conventional office display refreshes at 60 Hz, cycling through a full image scan every 16.67 milliseconds. In contrast, modern esports monitors and high-end laptop displays refresh at 120 Hz (8.33 ms), 144 Hz (6.94 ms), 240 Hz (4.17 ms), and up to 360 Hz (2.78 ms).

+-------------------------------------------------------------+
|               Frame Interval by Refresh Rate                |
|                                                             |
|   60 Hz   |================================> 16.67 ms       |
|  120 Hz   |================> 8.33 ms                        |
|  144 Hz   |=============> 6.94 ms                           |
|  240 Hz   |=======> 4.17 ms                                 |
|  360 Hz   |====> 2.78 ms                                    |
+-------------------------------------------------------------+

When your screen refreshes more frequently, two dramatic perceptual enhancements occur:

1. Motion Clarity and Reduced Ghosting: Objects moving across your field of view exhibit less display-induced motion blur, because the human eye tracks smooth continuous movement while the display presents shorter sample-and-hold durations.
2. Reduced Input Latency: The time delay between your physical mouse click or keystroke and the moment that action is visibly represented on screen shrinks substantially, granting competitive gamers a measurable reaction speed advantage.

How the LaptopXray High-Precision Tester Measures Screen Hz

Measuring display refresh rates directly inside a sandboxed web browser requires circumventing standard JavaScript timer jitter. Traditional setTimeout and setInterval primitives are throttled by operating system thread schedulers and cannot deliver sub-millisecond hardware accuracy.

Our Refresh Rate Engine achieves desktop-class benchmark precision through a four-stage measurement pipeline:

1. Hardware V-Sync Hooking via requestAnimationFrame

The engine registers a recursive callback via the standard window.requestAnimationFrame() API. In modern web engines (Blink, Gecko, WebKit), the browser compositor delegates the execution of requestAnimationFrame to the operating system’s native windowing compositor (DWM on Windows, Quartz Compositor on macOS, Wayland/X11 on Linux). This means callbacks are triggered in lockstep with the display’s physical vertical blanking interval (V-Blank).

2. Microsecond Hardware Clocks (performance.now)

Every rendered frame is timestamped using the high-resolution hardware monotonic timer performance.now(). Unlike Date.now(), which is susceptible to system clock drift and user time changes, performance.now() reports elapsed time with microsecond floating-point precision, unaffected by NTP updates.

3. Outlier Filtering & Median Delta Mathematics

To eliminate anomalies caused by background CPU context switching or garbage collection spikes, the engine records hundreds of consecutive delta intervals (Delta t = t_n - t_{n-1}) over a 3,000-millisecond duration. It discards anomalous edge frames and calculates the mathematical median frame interval. The exact refresh rate is derived using:

Refresh Rate (Hz) = \frac{1000}{Median Frame Interval (ms)}

4. Smart Standard Snap Mapping

Display controller timings frequently deviate by fractional percentages (e.g., 59.94 Hz or 143.98 Hz). The tool intelligently maps the floating-point measurement against standard VESA and CEA timings (60, 75, 90, 120, 144, 165, 240, 360, 480 Hz) while preserving the exact measured float for technical auditing.

Common Refresh Rate Standards and Hardware Requirements

Not every display cable or port can transmit high refresh rates. Use this reference matrix to verify your video output interface capabilities:

Troubleshooting: Why Is My High-Hz Monitor Stuck at 60 Hz?

If you purchased a 120Hz, 144Hz, or 240Hz monitor but our test reports exactly 60 Hz, walk through this definitive diagnostic checklist:

1. Windows Display Setting Misconfiguration

By default, Windows sets newly connected monitors to 60 Hz for compatibility reasons.

• Windows 11: Open Settings › System › Display › Advanced display. Select your high-refresh monitor from the top dropdown, then change the Choose a refresh rate option from 60 Hz to your panel’s maximum rating (e.g. 144 Hz or 165 Hz).
• Windows 10: Right-click Desktop › Display settings › Advanced display settings › Display adapter properties › Monitor tab › Screen refresh rate.

2. macOS ProMotion & External Monitor Configuration

• On macOS, open System Settings › Displays.
• If testing an external monitor or MacBook Pro built-in display, locate the Refresh Rate popup menu. Ensure it is set to ProMotion or the explicit numeric maximum (e.g., 144 Hertz), rather than 60 Hertz or 50 Hertz.

3. Display Cable and Port Bottlenecks

• Avoid HDMI 1.4 Hubs: Many USB-C laptop dongles and older HDMI splitters are limited to HDMI 1.4 specs, which cannot carry 1440p or 4K beyond 60 Hz.
• Prefer DisplayPort: For gaming PCs and laptops with USB-C/Thunderbolt video output, use a direct DisplayPort 1.4 cable or high-bandwidth USB-C to DP 1.4 adapter.

4. Browser Hardware Acceleration Disabled

If Hardware Acceleration is deactivated in your browser, the rendering thread falls back to CPU software rendering (SwiftShader), which caps animation frames at 60 FPS or causes severe micro-stutter.

• In Chrome / Edge: Go to chrome://settings/system and verify that “Use graphics acceleration when available” is toggled ON. Restart the browser.

High Refresh Rate vs Variable Refresh Rate (G-Sync & FreeSync)

A static high refresh rate updates the screen at rigid, fixed intervals regardless of when your GPU completes rendering a frame. However, in demanding games where GPU frame output fluctuates between 70 FPS and 130 FPS, fixed refresh rates lead to two annoying visual artifacts:

1. Screen Tearing: If V-Sync is OFF, the display draws part of an old frame and part of a new frame in the same scan cycle, creating a jarring horizontal tear line.
2. Stutter and Latency: If traditional V-Sync is ON, whenever the GPU drops below the target refresh rate (e.g., 143 FPS on a 144Hz screen), the display must repeat the previous frame, dropping perceived smoothness down to an integer division (72 FPS or 48 FPS) while introducing noticeable mouse lag.

Variable Refresh Rate (VRR) technologies—including NVIDIA G-Sync, AMD FreeSync, and VESA Adaptive-Sync—eliminate this compromise by allowing the monitor to dynamically adjust its refresh timing in real-time to match the GPU’s instantaneous frame rate.

After checking your refresh rate, explore our UFO Test for Motion Blur to observe pixel response times, verify synchronization with our Frame Skipping Test, and diagnose screen color fidelity using the Dead Pixel Test.