Site Isolation will be activated on Chrome after you restart. You can turn this feature off with the same steps but switch to Disabled. If something goes wrong, turn it off and use it normally.
Site Isolation increases memory usage on Chrome because it needs more processes. Google's benchmark benchmark also shows that using Site Isolation on the desktop makes the memory used increase from 10 to 13%.
If you use Firefox, don't forget that the browser has the same feature called First-Party Isolation.
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