Measure the cadence at which your browser is being given animation frames. The test samples frame intervals for several seconds, estimates the median browser-visible Hz, and shows timing jitter so you can spot obvious mode or throttling problems.
The browser schedules animation callbacks with requestAnimationFrame. Their spacing normally tracks the page's presentation cadence, which often follows the active display refresh mode.
The operating system may be set to another mode, a browser can throttle background/inactive work, battery saving can reduce cadence, and some display paths or remote sessions can cap presentation.
Minor variation such as 143–145 around a nominal 144 Hz mode is normal for a browser-based estimate.
At 60 Hz, an ideal frame interval is about 16.67 ms; at 120 Hz it is about 8.33 ms; at 144 Hz about 6.94 ms. The test reports spread in observed frame intervals rather than claiming input or pixel-response latency.
Large jitter can come from browser workload, CPU/GPU contention, window compositing or the test environment—not necessarily the monitor.
VRR displays can change their scanout cadence according to content and system behavior. A simple browser animation is not a full G-Sync/FreeSync validation suite and cannot prove the entire VRR operating range.
Refresh rate describes how frequently new frames can be presented. Pixel response time describes how quickly pixels transition. A high-Hz display can still have slow transitions or visible ghosting, so these are separate properties.
No. It only measures browser frame cadence. Change the actual display mode in your operating-system or graphics-driver settings.
Browsers intentionally throttle or pause animation callbacks in background tabs. Keep the test visible for a meaningful result.
No. It is a browser-observed estimate useful for troubleshooting and comparisons.