Refresh rate test

How to use the refresh rate test

1. Plug in your laptop or phone, and close games, videos and other busy tabs.
2. Click Start refresh rate test. Keep this tab visible and the window still.
3. Wait until Frame timing reads Stable. The refresh rate appears then, usually within a few seconds.
4. Watch the three squares. They move at the same speed, but one is redrawn 30 times a second, one 60 times a second and one at your screen’s full rate. The more often a square is redrawn, the smoother it moves.
5. Click Stop test when you are done. Measure again starts a new measurement.

The test runs until you stop it. Switching to another tab pauses it, and it starts again when you come back. To check a second screen, drag the window onto it and the test measures again. Pause motion stops the squares while the measurement goes on.

What the results mean

The big number is the rate your browser draws at, in Hz. A browser draws one frame per refresh of the screen that holds most of its window, so on most systems that is the refresh rate of your screen.

Frame time is the average time between two frames: about 16.7 ms at 60 Hz, 8.3 ms at 120 Hz, 6.9 ms at 144 Hz and 4.2 ms at 240 Hz. The page shows it only while the timing is stable.

Frame timing reads Stable when frames arrive evenly. The note under it then says how far 90% of frames stray from the frame time, in ms. When the timing is uneven, the page shows no rate, because an uneven measurement would only be a guess.

Dropped frames are frames that arrived at least one refresh late. A few while a page loads or when you switch apps are normal. A count that keeps rising means the device or the browser cannot keep up. Pauses of a second or more, such as a covered window, are not counted.

Variable refresh rate (G-SYNC, FreeSync, Adaptive-Sync) is invisible to web pages. This page cannot turn it on or tell whether it works.

Refresh rate test not working?

The test needs no permission, so it has few ways to fail. Most problems are a rate that is lower than expected or a reading that does not appear.

Browser not supported

The test needs requestAnimationFrame. If the page says that your browser does not support the test, update the browser or open the page in Chrome, Edge, Firefox or Safari.

No reliable reading

The page shows no rate when it cannot trust the timing, and the table above gives the fix for each of its three messages. A privacy setting such as Firefox’s resist-fingerprinting mode or Tor Browser is the usual cause of a rounded browser clock. On some systems a window that is not in focus runs slower, so click the page as well.

Stuck at 60 or 30 Hz

The test shows a list titled “Stuck at 60 or 30 Hz? Quick checks” under its results, with steps for Windows, Mac, Android, iPhone and iPad, power saving, cable and port, browser graphics acceleration and two monitors. The refresh rate your system is set to is under Settings > System > Display > Advanced display on Windows and under System Settings > Displays on a Mac. Change one thing at a time and press Measure again after each.

Shows about 30 Hz

Power saving is the usual cause, not the screen. Chrome’s Energy Saver, Edge’s efficiency mode and Low Power Mode on iPhone and iPad hold web pages at about 30 frames per second. On a 144 Hz or 165 Hz screen such a cap can show up as an odd value such as 28.8 or 27.5 Hz, and the page then notes a possible power-saving cap. Plug in the charger, turn power saving off and measure again.

The reading keeps starting over

The test starts over, and says why under Frame timing, when the screen or its settings change, when frames begin to arrive at another rate, or when the tab was hidden. A window dragged to another screen, a changed display setting and a laptop switching between AC power and battery all do this. Keep the window on one screen and wait for the next reading.

The squares do not move

If your device asks for reduced motion in its system settings, the squares stay still until you press Show moving squares, and then they are smaller and slower. Pause motion stops them at any time while the measurement goes on, and Play motion starts them again. Some screens lower their refresh rate while nothing on them moves, so with the squares still the reading can come out lower.

Rate history, phones and comparisons

Refresh rate over time charts the last 20 seconds, one reading a second. Steps in the line show the rate changing. Highest and Lowest count only steady seconds, and Now turns into Now (uneven) when the latest second was not steady. If the line settles at two different rates, your screen switches by itself (adaptive refresh), and a note under the chart says how to keep it high.

On a phone or tablet, a steady 60 Hz shows the verdict “This browser gets 60 frames a second” in place of “Expected more than 60 Hz?”. On Android, pick your phone’s manufacturer under Your phone for the settings steps that keep the screen at its high rate. This section does not appear on iPhone or iPad, where Safari’s engine sets the limit. After you change a setting, come back to the page or press Measure again: “Compared with your last test” then shows the change, such as 60 → 120 Hz.

How we measure

The test times every requestAnimationFrame callback, which a browser fires once per refresh of the screen that holds most of the window, and reads the gaps between them over the last 4 seconds, updating the numbers every 0.25 seconds. A rate appears only after at least 1.5 seconds and 45 frame gaps (3 seconds when frames come slowly), and only when at least 90% of the gaps last a whole number of frame times, at least 90% of single frames stray from the frame time by no more than 10% of it or 1 ms (whichever is larger), and the rate does not slide between the two halves of the window. The page then names the nearest common rate if the measurement is within 1% of it, and a frame counts as dropped when its gap is longer than 1.5 frame times. A web page cannot see the screen itself, so variable refresh rate (G-SYNC, FreeSync) and anything the system does after the browser draws a frame stay invisible, and the number is the rate this browser draws at.

Frequently asked questions

How do I check my monitor’s refresh rate?

Click Start refresh rate test and wait until Frame timing reads Stable, which usually takes a few seconds. The page then shows the rate your browser draws at, in Hz, which on most systems is your screen’s refresh rate. The rate your system is set to is in the display settings, for example under Advanced display on Windows.

How accurate is the refresh rate test?

The page times every frame your browser draws and shows a rate only when the timing is even. It averages many frames, so the measured value is usually within a fraction of a hertz of the rate the browser draws at. It cannot see past the browser, though. A browser that draws 60 frames per second on a 144 Hz screen reads as 60 Hz.

Why does my 144 Hz monitor show 60 Hz?

Usually because something between the monitor and the page is set to 60 Hz. Check the refresh rate in your system display settings, then the cable and port, then power saving, since laptops often drop to 60 Hz on battery. Safari on a Mac and every browser on an iPhone or iPad also keep web pages at 60 frames per second by default.

Can the test check G-SYNC or FreeSync?

No. A web page cannot switch variable refresh rate on or see whether it is active, and this test measures only the rate the browser draws at. To check it, use your monitor’s on-screen menu or a game with a frame rate counter.

Does the refresh rate test work on iPhone and Android?

Yes. Android phones with a 90 or 120 Hz screen can show the full rate, though some hold the browser at 60 Hz in battery saver mode. An iPhone or iPad shows 60 Hz, or 30 Hz in Low Power Mode, because every browser on it uses Safari’s engine, which limits web pages to 60 frames per second even on 120 Hz ProMotion screens.

Why does the 60 fps square look jerky on a 144 Hz screen?

Because 144 is not a multiple of 60, each frame of the 60 fps square stays on screen for two refreshes, then three, then two again. That uneven rhythm is the judder you see. On a 120 Hz or 240 Hz screen, 60 frames divide evenly into the refreshes, so the same square looks smoother.