A single bright line, nearly as tall as the lane, crosses a black field. It should stay in one piece from top to bottom. A tear cuts it at one height and shifts the lower part sideways.
Pattern
On a screen that holds each frame, your eye smears a shape at this speed across about 32 pixels.
Space pauses. The arrows change speed. F goes full screen.
Slow pan, 480 pixels a second8 pixels a frame at 60 Hz, 4 at 120 Hz and 2 at 240 Hz. A tear at this speed is only a small step. Use it to look again at a break you found at a faster speed.
Steady pan, 960 pixels a second16 pixels a frame at 60 Hz, 8 at 120 Hz and 4 at 240 Hz. A middle speed that most eyes can follow across the screen while still showing a clear step at a tear.
Fast pan, 1,920 pixels a second32 pixels a frame at 60 Hz, 16 at 120 Hz and 8 at 240 Hz. The page opens here. If two frames share the screen, the part of the line below the break sits one frame of travel away from the part above it.
Flick, 2,880 pixels a second48 pixels a frame at 60 Hz, 24 at 120 Hz and 12 at 240 Hz. The widest step at a tear, and the hardest speed for the eye to follow. Look at the middle of the screen and let the line pass.
Show all 16 speeds, patterns and signs (12 more)
Moving patterns 3
White line, 4 pixels wide, on blackA single bright line, nearly as tall as the lane, crosses a black field. It should stay in one piece from top to bottom. A tear cuts it at one height and shifts the lower part sideways.
Black line, 4 pixels wide, on whiteThe same line reversed, for a bright room or a screen where a white line on black is hard to follow.
Thin line, 2 pixels wide, white on blackA finer line. The step at a tear is the same width, so on a thin line it stands out more, but the line itself is harder to follow at the top speeds.
What you see, and what it means 4
A break in the line, with the lower part shifted sidewaysA tear. A new frame reached the screen outside the vertical blanking interval, the pause between two refreshes, so part of the screen still shows the frame before it and moving edges stop lining up.
A straight line from top to bottom at every speedNo tear reached this window. A browser draws each frame just before the screen repaints, and most desktops show windows through a compositor that keeps to the refresh. A game running with vertical sync off can still tear on the same screen, and no web page can show that.
A line that skips or stutters but stays straightNot a tear. Whole frames are arriving late or being dropped, so the picture jumps without splitting. Close other tabs and programs, then run the test again.
A smear or a faint copy behind the lineNot a tear either. That is the panel's pixels changing slowly, or your own eye following the motion. The line is still in one piece from top to bottom.
What to change, and how to check it 5
Vertical syncWith vertical sync on, a finished frame is shown only in the vertical blanking interval, so no tear is visible. Waiting for that moment can add delay, and stutter when the program cannot keep up with the screen. With it off, frames are shown as fast as they are made and may tear.
Variable refresh rateAlso called adaptive sync. The monitor adjusts its refresh rate to the frames it is sent, which lets games avoid tearing with less of the stutter that vertical sync can bring. It works only inside the range of rates the monitor supports.
A frame rate cap just under the refresh rateWith variable refresh rate on, one game engine's manual suggests leaving vertical sync on as well and capping the frame rate slightly below the monitor's highest refresh rate.
Desktop compositingSome window managers let you switch compositing off for speed, at the cost of tearing. If the line breaks in this test on a desktop like that, switch compositing back on and test again.
Full screen for the testGo full screen makes the line nearly as tall as the screen, so a break at almost any height is in view. In a small window a tear above or below the lane goes unseen.
How this list was compiled: Speeds, patterns, signs and settings written for this page on 2026-09-30; the moving shape is this site's own plain line. Pixels a frame is speed divided by refresh rate. Vertical sync showing an image only in the vertical blanking interval with no tearing visible, and tearing being possible with it off, are from the Godot Engine class reference, DisplayServer VSyncMode (https://docs.godotengine.org/en/stable/classes/class_displayserver.html). Vertical sync adding delay, asynchronous presentation trading tearing for lower latency, and synchronized presentation being the default on a composited desktop are from the Wayland tearing-control protocol (https://wayland.app/protocols/tearing-control-v1). Stutter with vertical sync, the frame rate cap with variable refresh rate, and window managers that can switch compositing off at the cost of tearing are from the Godot manual, Fixing jitter, stutter and input lag (https://docs.godotengine.org/en/stable/tutorials/rendering/jitter_stutter.html). Variable refresh rate, also called adaptive sync, letting the monitor adjust its refresh rate to the signal, removing tearing with less stutter, inside a limited range, is from the ArchWiki article Variable refresh rate (https://wiki.archlinux.org/title/Variable_refresh_rate). A browser calling a page's drawing code before the next repaint, at a rate that generally matches the display refresh rate, is from MDN, Window: requestAnimationFrame() (https://developer.mozilla.org/en-US/docs/Web/API/Window/requestAnimationFrame). All read 2026-09-30. The page measures nothing about tearing; the visitor judges the line by eye. Licence: own work
How it works
This screen tearing test slides one tall, thin line across the screen. Press Start and watch for a break in the line. It shows tearing that reaches the browser window; a game with vertical sync off can tear where this page does not.
Read the full guide
How to read the lines
Press Start, then Go full screen, and watch the whole line, top to bottom. A line that stays in one piece means no tear. A break, with the lower part shifted sideways, is a tear. A faster Speed widens the step: at 1,920 pixels a second and 60 Hz the two parts sit 32 pixels apart.
What a browser can and cannot show
A browser draws each frame just before the screen repaints, and most desktops show windows through a compositor that keeps to the refresh. So this screen tear test catches tearing on the desktop itself. It cannot see inside a game that runs with vertical sync off.
Two monitors? Drag the window to each one, reload the page and press Start; test both.
Seen a break? Open What to look for; the settings to try are under What to change, and how to check it.
Questions and answers
What does screen tearing look like?
A straight edge cut in two at some height, with the lower part shifted sideways. On this page the moving line breaks at that height. It needs motion to show: a still picture never tears.
What causes screen tearing?
A new frame reaching the screen outside the vertical blanking interval, the pause between two refreshes. Vertical sync holds each frame until that pause, which removes the tear and can add delay. Variable refresh rate lets the monitor follow the frame rate instead.
Why is there no tearing here when my game tears?
The page and the game reach the screen by different routes. The browser keeps to each refresh; a game with vertical sync off does not. Look for vertical sync or variable refresh rate in the game's settings or the graphics driver's.