VRR Flicker Test
Vary the rendering cadence on a gray field to watch for the brightness flicker some FreeSync/G-Sync displays show. Browsers can’t confirm VRR.
Some variable-refresh (FreeSync/G-Sync) displays flicker in brightness when the frame rate changes, especially on dark gray. This test deliberately varies the rendering cadence so you can watch for that flicker. Browsers can’t set or verify your actual refresh rate, so this is a subjective observation — not confirmation that VRR is on or a defect measurement.
How this test works
Display tests render precise patterns or measure timing directly in your browser. Color and pixel tests fill the screen with exact CSS colors so you can inspect the panel; gradient and sharpness tests draw fine structures that reveal banding or scaling.
Timing tests such as refresh rate and FPS sample requestAnimationFrame, which the browser calls once per display refresh. We discard warm-up frames, then report the median interval with a confidence level based on how consistent the samples are.
Full-screen tests use the Fullscreen API and hide all interface so nothing distracts from the panel. You can always exit with Escape, and reduced-motion preferences are respected for animated patterns.
How to use it
- Set your browser zoom to 100% so pixel-level patterns aren’t scaled.
- Start the test; for full-screen tests, use the on-screen or keyboard controls to change patterns.
- Inspect the whole screen carefully from a normal viewing distance.
- For timing tests, keep the tab in the foreground and let the sample finish.
- Press Escape or the exit button to leave full screen when you are done.
What it detects
- Dead or stuck pixels, and non-uniformity visible as color or brightness patches
- Banding in gradients and loss of detail in near-black or near-white patches
- A browser-observed estimate of refresh rate and rendering frame rate
- Your reported screen resolution, pixel ratio and color depth
What it can’t detect
- Laboratory-grade color accuracy, contrast ratio, or millisecond response time
- The panel’s true bit depth when the OS or browser reports a scaled value
- Whether variable refresh rate (VRR) or scaling is altering the result
Troubleshooting
| Symptom | What to do |
|---|---|
| Refresh-rate reading fluctuates | Bring the tab to the foreground, disable battery saver, and remember VRR displays vary by design. |
| Patterns look blurry | Set browser zoom to 100% and your OS display scaling to a native value. |
| Full screen won’t start | Some browsers require a direct click and disallow full screen in embedded contexts; try again with a direct interaction. |
| Can’t tell dust from a dead pixel | Clean the screen first, then inspect the same spot across several solid colors. |
FAQ
Why does my refresh rate reading fluctuate?
Browsers cap frames to the display refresh, and background throttling or variable refresh rate (VRR) can shift the estimate. We show a confidence level to reflect this.
Is this a calibrated color test?
No. It’s a visual inspection aid. True calibration requires a hardware colorimeter.
Can I test on my phone?
Yes, most display tests work on mobile in full-screen mode.
What’s the difference between a dead and stuck pixel?
A dead pixel stays black on every color; a stuck pixel stays lit on one color and sometimes recovers.
Why does resolution look different from what I expect?
Browsers report CSS pixels; multiply by the device pixel ratio for the physical pixel estimate. Browser zoom also changes the reported viewport.
Does the test change my monitor settings?
No. It only displays patterns and reads values your browser already exposes.
Related tests
Marching bars that step one pixel per frame reveal skipped frames as stutter or doubling — best judged with a phone camera photo.
Estimate how many times per second your display updates by sampling animation frames, with confidence and background-tab detection.
Track a moving object at adjustable speeds and backgrounds to inspect motion blur and ghosting. A visual check, not a millisecond measurement.