Google rolled out a new feature called Native Window Occlusion, to all Chrome installations on Windows in October 2020 with the release of Chrome 86. The company has published information on the performance benefits of the feature in a new blog post on the Chromium website.
Native window occlusion extends a feature in Chrome that limits the priority of background tabs to reduce browser resource usage and leave “more memory, CPU, and GPU for foreground tabs.” .
Google engineers noticed that some Chrome windows were completely covered by other windows, but their priority was not reduced. Google’s native window occlusion feature helps improve browser performance. Google notes that “almost 20% of Chrome windows are completely covered by other windows.”
Through experiments, we have found that almost 20% of Chrome windows are completely covered by other windows i.e. obstructed. If these occluded windows were treated as background tabs, our guess was that we would see significant performance gains. So, about three years ago, we started working on a project to track the occlusion state of every Chrome window in real time and lower the priority of tabs in occluded windows. We called this project Native Window Occlusion because we needed to know the location of native non-Chrome windows on the user’s screen.
Chrome monitors the occlusion status of each of the browser windows in real time to reduce the priority of open tabs in windows that are completely obstructed on Windows.
According to Google, performance has improved significantly in key areas with the activation of the bite check feature on Windows.
8.5% to 25.8% faster start-up
3.1% reduction in GPU memory usage
20.4% fewer render images drawn overall
4.5% fewer customers experiencing renderer crashes
3.0% improvement in time to first entry
6.7% improvement in First Content Paint and Largest Content Paint
The faster startup performance results from Chrome ignoring the occluded window’s work to save resources, which can benefit the foreground window.
Google also found that the feature reduced crashes by 4.5%.
All perks require that Chrome users have at least two Chrome browser windows open on their devices, and one of those windows is completely obstructed on the desktop.
Native window occlusion is only available in Chrome for Windows. Google is not revealing whether it will bring the feature to Chrome for Mac OS and Linux in the future.
The 20% figure of clogged Chrome windows seems pretty high, even if it only takes into account the scenarios where Chrome users have launched two or more Chrome windows on the Windows system.
Now you: how many browser windows do you usually use and how do you align them?