How sleeping tabs work
https://www.bleepingcomputer.com/news/microsoft/microsoft-edge-gets-a-performance-boost-with-sleeping-tabs/
Microsoft is rolling out a sleeping tabs feature to the new Chromium-based Edge web browser which will drastically reduce memory and CPU resource usage.
The new feature is being deployed to all users running Microsoft Edge Beta 88 after its initial unveil, in September, as a Microsoft Edge experiment.