Screen Refresh Rate Tester
/test/Live Hz & FPS Counter · Frame Jitter Oscilloscope · Multi-Lane UFO Pursuit Ghosting · 100% Client-Side
Frame: 0.00 ms
Excellent frame stability
0% drop rate
Range: -- - -- Hz
How Browser Refresh Rate Measurement Works:
Modern operating systems bind window.requestAnimationFrame() directly to your GPU’s V-Sync hardware clock. By benchmarking microsecond delta intervals across 120 rolling frames, this test computes your panel’s physical refresh frequency (60Hz, 120Hz, 144Hz, 240Hz, or 360Hz) with 99.9% precision.
How to Use the Screen Refresh Rate & UFO Ghosting Tester: Step-by-Step Guide
- Step 1 (Benchmark Display Refresh Rate): Open the Refresh Rate (Hz) tab and review the live frequency readout. The browser clocks your GPU V-Sync interval across 120 rolling frames to verify whether your display is actively running at 60Hz, 120Hz, 144Hz, 240Hz, or higher.
- Step 2 (Evaluate UFO Motion Blur & Ghosting): Switch to the UFO Motion Blur tab. Adjust the speed presets (e.g., 960 px/sec) and track the animated spacecraft smoothly with your eyes horizontally. Contrast the top full-rate lane against the lower half-rate lanes to benchmark retinal persistence and frame pacing.
- Step 3 (Inspect Frame-Time Jitter & Tune Overdrive): Use the Frame Pacing Jitter oscilloscope to detect micro-stutters. Then refer to the Overdrive & MPRT Guide to adjust your monitor’s OSD response time setting, eliminating dark ghosting trails or glowing overshoot halos.
The Physics of Display Refresh Rates: Understanding Hertz (Hz) vs Frame Rate (FPS)
The refresh rate of a physical display screen, quantified in Hertz (Hz), defines the exact frequency at which the monitor’s hardware panel redraws its liquid crystal, OLED, or quantum dot pixel matrix. A standard 60Hz display scans the panel 60 times every second (once every 16.67 milliseconds), whereas modern high-performance gaming displays scan at 144Hz (every 6.94ms), 240Hz (every 4.17ms), 360Hz (every 2.78ms), and up to 540Hz (every 1.85ms).
While users often conflate Refresh Rate (Hz) with Frame Rate (FPS), they represent two decoupled stages in the graphics pipeline. Frame rate is an application-side metric indicating how quickly your GPU and graphics engine construct new visual buffers. Refresh rate is a display-side hardware clock indicating when the monitor transfers the active framebuffer to physical photons. When your GPU produces frame rates exceeding the refresh rate without variable sync, horizontal screen tearing occurs. Conversely, when frame delivery is sporadic or delayed, stuttering degrades visual fluidity.
| Display Refresh Rate | Frame Window (ms) | Retinal Persistence (MPRT) | Optimal Use Case | Recommended Interface |
|---|---|---|---|---|
| 60 Hz | 16.67 ms | 16.7 ms (High Blur) | Office work, casual video playback | HDMI 1.4 / DisplayPort 1.2 |
| 120 Hz / 144 Hz | 8.33 ms / 6.94 ms | 7.0 ms (Crisp Motion) | Competitive gaming, smooth OS UI | HDMI 2.0 / DisplayPort 1.2+ |
| 240 Hz | 4.17 ms | 4.2 ms (Very Clear) | Esports FPS (Valorant, CS2, Overwatch) | DisplayPort 1.4 DSC / HDMI 2.1 |
| 360 Hz – 500 Hz | 2.78 ms – 2.00 ms | 2.0 ms (Near-Zero Smear) | Pro tournament esports arenas | DisplayPort 2.1 UHBR10+ |
The UFO Pursuit Motion Blur Test: Eye-Tracking Persistence & Response Time (MPRT vs GtG)
Why do moving objects appear blurred even on high-end displays? Most modern LCD and OLED screens utilize a sample-and-hold display architecture. Unlike historic cathode ray tube (CRT) monitors or pulsed strobed displays that flash a frame for a microsecond before returning to black, sample-and-hold monitors continuously emit light and hold the image static across the entire duration of the frame interval.
When your eyes track a target traveling smoothly across the screen (such as the UFOs in the interactive test above), your retinas move continuously across the stationary held frame. This physical mismatch projects the held image across multiple neighboring photoreceptors on your retina, generating eye-tracking motion blur (retinal smear). This phenomenon is governed by Motion Picture Response Time (MPRT) rather than pixel transition speed (GtG):
Grey-to-Grey Response Time (GtG)
The time in milliseconds required for a physical pixel to transition from one shade of gray to another. Slow GtG transitions result in dark ghosting trails as liquid crystals lag behind the video signal. While modern OLEDs achieve ultra-fast 0.03ms GtG, motion blur still persists unless the refresh rate is dramatically increased.
Motion Picture Response Time (MPRT)
The perceived optical blur duration seen by human retinas during continuous pursuit tracking. On non-strobed sample-and-hold panels, MPRT is mathematically bounded by frame persistence: exactly 16.7ms at 60Hz, 6.94ms at 144Hz, and 4.17ms at 240Hz. Doubling refresh rate cuts retinal blur in half.
How to Calibrate Monitor Overdrive: Eliminating Ghosting and Overshoot Coronas
To accelerate liquid crystal reorientation on IPS and VA panels, monitor manufacturers implement voltage boosting known as Overdrive (Response Time Compensation / RTC). By applying an initial spike of overvoltage, molecules rotate to their new color coordinates faster than normal passive charging allows.
However, tuning overdrive requires careful balance:
- Under-Overdrive (Ghosting / Trailing): When overdrive is disabled or set too low, pixel transitions cannot complete within the refresh window. Fast-moving objects leave dark, smeared trails behind them.
- Optimal Overdrive: Liquid crystals reach their target state within ~1–2ms without excess momentum. Moving edges appear crisp and clean with zero halos.
- Over-Overdrive (Inverse Ghosting / Pixel Overshoot): When overdrive voltage is excessively aggressive ("Extreme" or "Fastest" modes), pixels surge past their target brightness before recoiling. This produces bright cyan or white halos trailing behind dark objects, severely degrading image quality.
Frequently Asked Questions About Screen Refresh Rates & Motion Testing
How does this online tool measure my screen refresh rate (Hz)? ↓
This tool interfaces directly with the browser’s native window.requestAnimationFrame() rendering engine. In modern operating systems and web browsers (Google Chrome, Microsoft Edge, Mozilla Firefox, Safari), the requestAnimationFrame callback is hardware-synchronized to your GPU’s V-Sync clock. By recording microsecond-accurate hardware timestamps using high-resolution performance.now() across 120 rolling frame intervals, the tool calculates the exact physical refresh rate of your active monitor (e.g., 60Hz, 75Hz, 120Hz, 144Hz, 165Hz, 240Hz, 360Hz, or 500Hz) with 99.9% precision.
Why does my 144Hz or 240Hz monitor report only 60Hz in the test? ↓
If a high-refresh-rate monitor reports only 60Hz, it is almost always due to an operating system display setting, browser hardware acceleration, or cable limitation. On Windows, right-click the desktop, select Display Settings → Advanced Display, and ensure the "Choose a refresh rate" dropdown is explicitly configured to your panel’s maximum rating (e.g. 144Hz or 240Hz). Additionally, verify that Hardware Acceleration is enabled in your browser settings (under System/Performance), and confirm you are connected via DisplayPort or HDMI 2.0/2.1, as older HDMI 1.4 ports cap bandwidth to 60Hz at higher resolutions.
What is the UFO Motion Blur & Ghosting test, and what should I look for? ↓
The UFO Pursuit Motion Blur Test is the gold-standard visual benchmark for evaluating display pixel response times and motion clarity. As the stylized UFO spacecraft move across the screen horizontally at synchronized speeds (e.g. 960 px/sec), track them smoothly with your eyes. On high-refresh-rate displays with fast pixel response, the spaceship body, windows, and pilot remain sharp and legible. If you observe dark, blurry smearing dragging behind the UFO, your monitor has slow pixel transitions (ghosting). If you see bright white or inverted halos trailing behind it, your monitor’s overdrive voltage is pushed too high (overshoot).
What is the difference between Refresh Rate (Hz) and Frame Rate (FPS)? ↓
Refresh Rate (measured in Hertz / Hz) is the hardware frequency at which your physical display panel redraws a new picture on the screen each second (e.g., 144 times per second on a 144Hz monitor). Frame Rate (measured in Frames Per Second / FPS) is the speed at which your graphics card (GPU) and software application render and output new frame buffers. For optimal smoothness without tearing or stutter, your GPU should output frame rates that match or exceed your monitor’s refresh rate, ideally synchronized via technologies like G-Sync, FreeSync, or V-Sync.
What causes frame-pacing jitter and micro-stutter? ↓
Even if a monitor is capable of high refresh rates, micro-stutters occur when consecutive frames are delivered at irregular time intervals. For a perfectly fluid 144Hz experience, every single frame must arrive exactly 6.94 milliseconds apart. If one frame takes 3ms and the subsequent frame takes 14ms, the average frame rate may still read 144 FPS, but human vision perceives a jarring hitch or stutter. Causes of frame-pacing jitter include background CPU spikes, browser thread contention, mismatched multi-monitor refresh rates, or GPU compositor delays.
How do I fix monitor ghosting or inverse overshoot coronas? ↓
You can tune pixel response by accessing your monitor’s physical On-Screen Display (OSD) menu using the buttons or joystick on the back/bottom of your panel. Look for a setting named Response Time, Overdrive, TraceFree, or Response Time Compensation (RTC). If you see dark ghosting trails, increase the overdrive setting from "Off" or "Standard" to "Fast". If you see bright white glowing halos (inverse ghosting), your overdrive is set too high—reduce it from "Extreme" or "Fastest" down to "Normal" or "Fast".