:visitedselectors in order to prevent websites from stealing your browsing history.
It is widely believed that techniques such as cache timing may theoretically offer comparable insights, but the attacks demonstrated so far seemed unconvincing. Among other faults, they relied on destructive, one-shot testing that altered the state of the examined cache; produced only probabilistic results; and were far too slow and noisy to be practically useful. Consequently, no serious attempts to address the underlying weakness have been made.
My proof of concept is fairly crude, and will fail for a minority of readers; but in my testing, it offers reliable, high-performance, non-destructive cache inspection that blurs the boundary between
:visited and all the "less interesting" techniques.