Same URL navigations don’t normally increase history.length, But this allows the opener to check the exact URL of a window. So in Chromium this is no longer true for a cross-origin initiator if there’s no error, there are currently timing attacks with same document navigations however. https://chromium-review.googlesource.com/c/chromium/src/+/2983325 Also 40087397 - Eliminate :visited privacy issues once and for all - chromium still exists and should be fixed.