Screen tearing is a visual anomaly that may occur when a monitor refreshes its display: one or more horizontal "tear lines" appear on the screen, with the upper and lower portions of the same frame misaligned. This is especially noticeable during fast camera movement or high-speed webpage scrolling. Many users mistakenly believe this is caused by insufficient GPU performance or a damaged monitor, but in reality, screen tearing is a normal phenomenon caused by the mismatch between the GPU's output frame rate and the monitor's refresh rate.

This article will help you understand the causes of screen tearing, and use online detection tools such as TestUFO to observe tearing lines through moving vertical bars and high-speed scrolling images, helping you determine whether your monitor has significant screen tearing issues and how to specifically improve display smoothness.

1. How Screen Tearing Occurs

The monitor refreshes its display at a fixed frequency (for example, 60Hz, 144Hz, 240Hz), while the GPU outputs frames at a dynamically changing rate. If the GPU updates the frame data while the monitor is in the middle of a refresh cycle, the monitor will simultaneously display content from two consecutive frames within the same refresh, resulting in a horizontal tearing line at the moment of frame transition.

Common triggering scenarios include:

  • Game frame rate significantly higher than refresh rate: The GPU renders too quickly for the monitor to complete a full refresh, often resulting in multiple tearing lines.
  • Game frame rate lower than refresh rate: Unstable frame generation intervals can also cause misalignment between frames and refresh cycles.
  • Windowed mode or video playback: The desktop compositing environment is complex, and tearing can be more noticeable in certain scenarios compared to exclusive fullscreen.

2. Preparations Before Online Testing

To obtain accurate results, it is recommended to complete the following preparations before testing:

  • Disable browser power-saving throttling: Some browsers reduce animation frame rates in the background or in power-saving mode, which can affect test accuracy.
  • Use a browser that supports high refresh rates: The latest versions of Chrome, Edge, or Firefox typically sync correctly with the monitor's refresh rate.
  • Run the test page in fullscreen: Press F11 to enter fullscreen mode to avoid desktop compositing interference, making the test closer to exclusive fullscreen conditions.
  • Disable vertical sync-related settings: Temporarily disable V-Sync and G-Sync/FreeSync in the GPU driver and games to observe native tearing conditions.

3. Using TestUFO to Observe Moving Vertical Bars and Tearing Lines

TestUFO is the most commonly used online tool for monitor refresh rate and screen tearing detection. It exposes tearing issues through high-speed moving vertical bars or grids. The steps are as follows:

  • Open TestUFO's Frame Skipping or Blur Busters UFO test page: The page will display one or more horizontally moving UFO icons or vertical bars.
  • Observe the edges of moving objects: Under normal synchronized conditions, the edges of moving objects should remain continuous and smooth without obvious horizontal breaks; if you see vertical misalignment or a horizontal tear line spanning the screen, that is screen tearing.
  • Adjust the browser window size: Changing the window size or zoom level can alter the position and visibility of tearing lines, helping confirm whether the issue is caused by refresh rate and frame rate mismatch.
  • Switch between different refresh rates: If your monitor supports multiple refresh rates, test at 60Hz, 120Hz, and 144Hz respectively to observe whether the number of tearing lines decreases.

4. Auxiliary Detection Through High-Speed Scrolling Images

In addition to TestUFO, high-speed scrolling in everyday scenarios is also suitable for detecting screen tearing. Open a long article or image list and quickly scroll up and down with the mouse wheel, observing whether the following phenomena occur as content moves:

  • Horizontal tearing lines: Text or images on the page briefly misalign horizontally during scrolling, as if "cut" into upper and lower sections.
  • Content judder or ghosting: In non-smooth scrolling mode, text edges appear blurry or broken during fast scrolling, indicating that frame updates are not synchronized with the monitor's refresh.
  • Jumping when scroll direction changes: When switching between scrolling up and down, the image may briefly tear, which is typically related to the system compositor and browser rendering strategy.

If these phenomena improve significantly after disabling browser hardware acceleration, the issue is related to the GPU compositing path; if they persist, it is more likely a mismatch between the monitor's refresh rate and content frame rate.

5. How to Improve Screen Tearing

After confirming the presence of screen tearing, you can adjust settings in the following order:

  • Enable Vertical Sync (V-Sync): Enable V-Sync in games or GPU drivers to force the GPU to wait for the monitor's refresh cycle, which can essentially eliminate tearing but may increase input latency.
  • Use G-Sync / FreeSync: If your monitor and GPU support variable refresh rate technology, enabling it allows the monitor to dynamically match the GPU's output frame rate, fundamentally reducing tearing and stuttering.
  • Limit game frame rate: Cap the game frame rate at or below the monitor's refresh rate to avoid multiple tearing lines caused by excessively high frame rates.
  • Adjust the monitor refresh rate: Set the refresh rate to the highest value supported by your monitor in system display settings; a higher refresh rate shortens the visible duration of tearing.
  • Update GPU drivers and browser: Newer drivers and browsers typically optimize compositor synchronization strategies, reducing tearing in desktop and video playback scenarios.

6. Summary

Screen tearing is not a monitor hardware failure but rather a manifestation of frame rate and refresh rate desynchronization. Through TestUFO's moving vertical bars and everyday high-speed page scrolling, you can quickly assess the severity of tearing issues, then optimize by combining vertical sync, variable refresh rate, or frame rate limiting. For average users, enabling G-Sync/FreeSync or limiting frame rate is usually the most effective solution; for those primarily using their computers for office work and web browsing, disabling browser hardware acceleration or adjusting the refresh rate can also bring noticeable improvements.