Refresh Rate (Hz) Detector
Measure the frame rate your browser is actually presenting, and what is capping it.
Keep this tab in front for the full three seconds. A browser slows animation frames right down in a background tab, and that would be measured as a slow display.
How this test works
The test records the gap between animation frames for three seconds and takes the median, then converts it to a rate and matches it against the rates panels are actually sold at. The median is the important choice: one garbage-collection pause or a window switch produces a single 400 ms gap, and an average would turn that into a permanently slow display. Long frames are counted separately and reported as what they are. If the intervals vary too much to support a single rate — a variable-refresh display, or a machine busy with something else — the tool says so instead of naming one.
What the results mean
- Presentation rate
- How often the browser delivered a frame to this tab. This is the honest measurement. Where it is lower than your panel rating, the cap is between the two — the OS display setting, a power profile, the cable, or the browser.
- Matches panel rate
- The nearest rate panels are sold at, within 2%. A reading between the standard rates usually means throttling or a variable-refresh display.
- Frame-to-frame jitter
- How consistently frames arrive. Steady output sits near zero; large jitter is stutter you can see even when the average rate looks fine.
- Long frames
- Gaps of at least two frame periods — a deadline the browser missed. A handful over three seconds is normal on a busy machine; a stream of them is not.
Common problems and fixes
- My 144 Hz monitor reads 60 Hz
- Check the refresh rate in your OS display settings — a high-refresh monitor plugged in for the first time almost always defaults to 60 Hz. If it is already set higher, check the cable and port: older HDMI carries the resolution but not the rate.
- The result changes every time I run it
- Something else on the machine is competing for the GPU, or the display is variable-refresh. Close other windows, keep this tab in front, and take the reading with the most frames and the least jitter.
- It says the timing was too irregular
- That is usually adaptive sync doing its job on a nearly static page, or a background process interfering. It is a refusal to guess rather than a fault.
- My laptop reads lower on battery
- Expected. Battery-saver profiles cap both the panel and the compositor. Run it on mains power for the real number.
Frequently asked questions
How do I check my monitor refresh rate?
Run the test above for a genuine measurement of what the browser is receiving, then compare it with the rate set in your operating system display settings. The two disagreeing is itself the useful result: it means something between the panel and the page — the OS setting, a power profile, the cable, or a second display — is holding the rate down.
Why is my refresh rate lower than my monitor supports?
The four usual causes, in the order worth checking: the OS is still set to 60 Hz because that is the default on a new connection; the machine is on battery and running a power-saving profile; the browser window is on a slower second display; or the cable or port cannot carry the higher rate at that resolution. All four are fixable without buying anything.
Is this the same as my monitor refresh rate?
Not necessarily, and the difference matters. What is measured is how often the browser presents a frame to this tab, which can only ever be equal to or lower than the panel rate. Reading 60 Hz on a 165 Hz panel is a real result — it means something is capping you at 60 — but it is not evidence that the monitor is faulty.