The startup boost feature maximizes Microsoft Edge’s performance on Windows 10 by launching certain browser processes when a device is powered on. This allows the Chromium browser to exist in a “state of readiness”. In Microsoft Edge 89, startup boost is automatically enabled without user interaction and Microsoft claims it can improve startup times by 29 to 41 percent.
Unfortunately, after Microsoft automatically enabled startup boost, some users started reporting performance issues, including a bug where closing the Edge window doesn’t quit the browser and it will relaunch again. It will also continue to run in the background — something you might never notice unless you open Task Manager.
Microsoft claims that it has taken note of the feedback and has gone to work to identify the source of the bug so that it can be fixed as soon as possible. It said in a public notice: "Our team is working on fixing a couple of issues where some customers are seeing the browser reopen immediately after exiting and/or a message about reopening tabs when startup boost is enabled."
Users can still enable the feature if they go to Edge > Setting > System and toggle the Startup boost button. Additionally, Microsoft encourages users to keep submitting feedback on this feature, which helps them improve it.