See this chromium issue: https://bugs.chromium.org/p/chromium/issues/detail?id=773307 The user is requesting that we don't update a service worker if the page is blocked from loading with X-Frame-Options:Deny. Right now, though, the spec does require firing an update and we don't always do it. Right now we trigger navigation based updates from DOMContentLoaded which is why we probably don't update in this case. This is a minor issue, but something to think about as we move service workers into a separate process and have to refactor updates.