Refresh Rate Test
The hertz your browser actually draws at, with frame time and missed frames.
Keep this window in front while the test runs: a hidden or background window is given far fewer frames.
Press Start and the measured rate appears here.
Frame times
Every frame of the run, grouped by how long it took. One tall bar is a steady display; a tail to the right is frames the browser missed.
| Frame time | Frames | Share of frames |
|---|---|---|
| No measurement yet. | ||
About the Refresh Rate Test
This measures how often your browser is actually able to draw, in hertz, by timing a run of animation frames on this page. It is the rate that decides whether scrolling and games look smooth — and it is not always the number on the box: a browser window on a 144 Hz screen can be drawing at 60 Hz because of a battery saver, a power setting, an external monitor running at its default rate, or another window asking for the graphics card.
As well as the rate you get the frame time (how many milliseconds each frame took), the jitter (how much that varied), and how many frames were missed. A display can report a high rate and still stutter; the jitter column is where that shows up.
The measurement is a browser measurement, which is what matters for anything you do in a browser. Nothing is installed, nothing is uploaded, and the test runs entirely on your device.
How to use it
- Pick how long to measure — 3 seconds for a quick look, 10 or 30 seconds to catch stutters that come and go.
- Press Start and leave the page in front: a window that is hidden or in a background tab gets far fewer frames, and the result would be meaningless.
- Read the hertz at the top, and the standard rate it matches when it matches one. If none matches, something is limiting the frames.
- Check the frame time and jitter below, and the bar chart of frame times: one tall bar is a steady display, a long tail means missed frames.
- Run it again on battery and on mains, or with other windows closed, to see what is holding the rate down. Copy result puts the numbers on your clipboard.
Examples
10 seconds of frames
60.0 Hz · median frame time 16.67 ms · jitter 0.1 ms · frames missed 0
10 seconds of frames
60.0 Hz — the panel can do 144 Hz, so the rate is set in the operating system’s display settings, not here
3 seconds of frames
41.3 Hz — not close to a standard rate, so frames are being limited (battery saver, a background window, or a browser throttling the page)
What the numbers mean
- Hertz (Hz) — frames the browser drew per second, taken from the median gap between frames, so one long pause cannot drag the figure down. A standard rate is noted beside it only when the measurement is within 2.5 % of one.
- Median frame time — the typical gap in milliseconds: 16.67 ms is 60 Hz, 8.33 ms is 120 Hz, 6.94 ms is 144 Hz.
- Fastest and slowest frame — the shortest and longest gap in the run. A slowest frame many times the median is a visible stutter.
- Jitter — how far the gaps sat from the median on average. Under about 5 % of the frame time is as steady as a browser gets.
- Frames missed — gaps at least one and a half times the median, which means at least one frame never arrived.
- Average fps — frames ÷ seconds over the whole run, so it drops when frames are missed while the hertz figure stays put. The gap between the two is the stutter.
Why the browser may show less than your screen can do
A browser draws at the rate the system gives it, and several things cap that:
- the refresh rate chosen in the operating system’s display settings, which is often not the panel’s highest;
- a battery saver or a power plan, which can lower the rate a laptop draws at while it runs on battery;
- an external monitor or a docking station running at a default rate over a cable that cannot carry more;
- a background tab or a window that is not on screen: browsers deliberately cut frames there to save power;
- heavy work in another tab or application, which shows up as jitter and missed frames rather than a lower rate.
So a low reading here is a real measurement of what this browser can draw — it is just not always a measurement of the panel. Change the rate in the display settings, then run the test again.
Limitations
- This measures what the browser draws, not what the panel is set to. A browser cannot read the display’s own refresh rate.
- A hidden window or a background tab gets far fewer frames on purpose; keep the page in front while it runs.
- Some browsers round frame timestamps for privacy, which puts a small floor under the jitter figure.
- Variable-refresh displays (FreeSync, G-Sync) change rate as they go, so the reading is the average behaviour over the run, not a fixed panel rate.
Privacy
The timings stay in this browser: nothing about your display or your device is uploaded, and the page keeps nothing after you close it.
Frequently asked questions
Why is the result 60 Hz when my monitor is 144 Hz?
Because something between the panel and the browser is capping it: the refresh rate selected in the operating system’s display settings, a battery saver or power plan, a cable or dock running at a default rate, or the window not being the active one. Change the rate in the display settings and run the test again.
Is this the same as a frame-rate counter in a game?
No. A game draws as fast as it can and may exceed the display rate; a browser draws once per display refresh, so this measures the refresh rate the browser is given. It is the right number for scrolling, animations and anything running in a browser.
What is a good jitter figure?
Under about 5 % of the frame time — roughly 0.8 ms at 60 Hz — is as steady as a browser gets. Up to 15 % is normal on a busy machine. Above that, frames are being missed often enough to see.
Does the test need an install or an extension?
No. It times the browser’s own animation frames on this page, so it works in any modern browser on a phone, tablet or computer with nothing to install.