Screen Tearing Test

What is this tool?

Tearing is what you see when the display refreshes part-way through a new frame: the top of the screen shows one frame and the bottom shows the next, so a moving image looks split along a horizontal line.

This test scrolls a high-contrast pattern at a frame rate you choose. Setting a target FPS that does not divide evenly into your refresh rate is the reliable way to provoke tearing, which is why the FPS control goes from 30 up to 240.

It is a visual test. The tool creates the conditions and you say whether the split is there — a browser has no way to inspect the compositor's synchronisation.

How to use it

1. Go fullscreen firstThis matters more here than on any other display test. Browsers often composite windowed content with vertical sync applied, which hides tearing entirely. Fullscreen frequently exposes it. The page has a section on exactly this: “Why Fullscreen Can Change Results”.
2. Pick a preset, then a speedStandard · 960 px/s is the starting point; Precision · 240 px/s and Stress · 1920 px/s bracket it. The ladder is 120, 240, 480, 960 and 1920 px/s. Faster motion makes a tear line easier to see because the offset between halves grows.
3. Set a target FPS that fights your refresh rateOptions are 30, 60, 75, 120, 144, 165 and 240 FPS. On a 60 Hz display, 75 or 144 FPS is far more likely to tear than 60, because the frames stop lining up with the refreshes. Sync Comparison puts a synchronised and an unsynchronised pattern together.
4. Watch for a horizontal break during motionA tear is a straight horizontal line where the image above and below no longer align. It moves up or down the screen rather than staying in one place. Pause freezes the pattern if you want a closer look; Run Again repeats the run.
5. Record what you sawThe self-report labels are “Motion appears continuous”, “I can see a horizontal break”, “The image appears split during movement”, “The upper and lower parts appear out of alignment”, “The artifact changes with speed”, “The artifact changes with fullscreen”, “The artifact changes with target FPS” and “Motion remains synchronized”. The last three are the diagnostic ones — an artefact that changes with FPS or fullscreen is tearing.

What the results mean

Motion appears continuous

No tearing under these conditions. Try a target FPS that does not divide into your refresh rate, and try fullscreen, before concluding the setup never tears — vertical sync may simply be doing its job.

A horizontal break during movement

That is tearing. The display refreshed while a new frame was still being written. It is a synchronisation problem between the renderer and the display, not a panel defect.

The artefact changes with target FPS

Strong confirmation that it is tearing. A panel fault would not care what frame rate the page is rendering at. This is why the FPS control exists.

The artefact changes with fullscreen

Also confirmation. Windowed and fullscreen content often take different compositing paths, one of which applies vertical sync. A defect in the display would look the same either way.

Motion remains synchronized

Frames and refreshes are aligned — vertical sync, or a variable-refresh display keeping the panel in step with the frame rate. Note that adaptive sync only works inside the panel's supported range; outside it, tearing can return.

What it can detect

• Tearing during horizontal scrolling at a known frame rate
• Whether tearing depends on the target frame rate, which distinguishes it from a panel artefact
• Whether fullscreen and windowed compositing behave differently in your browser
• Whether vertical sync appears to be active for this content
• Tearing that persists at high frame rates — the page covers this under “Why Tearing Changes at Different FPS”

Limits worth knowing

A browser can only report what the platform gives it. These are the honest boundaries of this page, so a result is never read as more than it is.

• The page has both a “Browser Test Limitations” section and the FAQ “Can a browser detect screen tearing automatically?” It cannot. There is no API that reports a torn frame; the tear is something only your eyes can confirm.
• It also cannot confirm GPU vertical sync — another question the page's FAQ raises directly. What the test shows is how this page behaves in this browser, which is not the same as how a native game behaves.
• Browser compositing may apply its own synchronisation regardless of the target FPS you pick, so an absence of tearing here does not guarantee an absence of tearing in other applications.
• The test draws ordinary moving graphics and cannot damage a display. The page states this in its FAQ.

Tips

• Use a target FPS deliberately mismatched to your refresh rate. 75 FPS on a 60 Hz panel provokes tearing far more reliably than 60 FPS does.
• Watch the middle third of the screen. A tear line can appear anywhere, but the centre is where it is easiest to notice against a scrolling pattern.
• If you enable G-SYNC or FreeSync, retest at a frame rate below the panel's minimum supported rate. That is where adaptive sync stops helping.

Troubleshooting

Related documentation

• DisplayDisplay FPS TestMeasure the frame rate your browser is actually delivering, with 1% lows and jitter.
• DisplayRefresh Rate TestEstimate your display's refresh rate from frame timing, with a confidence level attached.
• DisplayMotion Blur TestMoving patterns at controlled speeds, so you can judge how sharp motion stays.
• DisplayScreen Ghosting TestHigh-contrast moving patterns that make trails and overshoot easy to see.
• DisplayDisplay Response Time TestControlled colour transitions for judging pixel response, trailing and overshoot by eye.