Contact emails fer...@chromium.org, kenjibah...@chromium.org
Explainer https://github.com/fergald/docs/blob/master/explainers/permissions-policy-deprecate-unload.md Specification https://github.com/whatwg/html/pull/7915 Summary A Permission-Policy for creating unload event listeners will be added. Initially, the default policy will be set to allow. From there, Chrome will gradually migrate the default policy to deny (i.e. increasingly disallow the creation of unload event listeners, eventually reaching a state where deny fully becomes the default policy). The ultimate goal is to remove support for unload event. Blink component Blink>PermissionsAPI <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EPermissionsAPI> Motivation The unload event is extremely unreliable. It is ignored in most cases by all mobile browsers except Firefox on Android. Furthermore, in Safari, the unload event is ignored on both desktop & mobile platforms. In the current state, unload is a major BFCache blocker (~18 percentage points reduction of hit rate for Chrome). The change will unlock a large fraction of that hit-rate while providing an opt-out for those who need more time to migrate. It also sends a clear signal that unload should not be used in new development. Sidenote: the spec was changed to say that unload should only run if the page cannot enter BFCache, which reflects Safari’s behavior, However neither Chrome nor Mozilla have implemented this behavior. In Chrome's case, we believe that this would suddenly break various sites and would make it hard for developers to know if/when unload may run. Initial public proposal None TAG review https://github.com/w3ctag/design-reviews/issues/738 TAG review status Pending Risks Interoperability and Compatibility If no other browsers implement this, there is a risk that devs continue to use unload widely and pages malfunction on chrome. However given that alternatives to unload exist it seems entirely possible for sites that are actively maintained to move off unload. Gecko: ( https://github.com/mozilla/standards-positions/issues/691#issuecomment-1484997320) It's possible that pages are depending on `unload` handlers in subframes for functionality even without any main frame navigation. We should try to understand how common this is before breaking it. It should be possible to measure how often subframe unloads fire when the mainframe is not navigating. This will give us an upper bound on the size of the problem, - Chrome: we have landed code to measure the occurrence of unload in different scenarios. We will report back the findings. WebKit: https://github.com/WebKit/standards-positions/issues/127 Web developers: Positive ( https://groups.google.com/a/chromium.org/g/bfcache-dev/c/zTIMx7u4uxo/m/-M4IS6LDBgAJ) The web communities we reached out had positive reactions to our proposal and we have not heard about any concrete blockers. Other signals: WebView application risks Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications? On WebView, we will introduce the Permissions-Policy but not move the default to "deny". BFCache does not work on WebView, so the benefit is lower. Meanwhile the risk seems higher as we have far less visibility into the HTML being run in WebViews. A roll-out to WebView should be done independently and in consultation with the WebView team. Debuggability None Is this feature fully tested by web-platform-tests <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> ? Yes Flag name None Requires code in //chrome? False Estimated milestones M115 for availability of Permissions-Policy M115 is the earliest we would start to disable unload, however Link to entry on the Chrome Platform Status https://chromestatus.com/feature/5579556305502208 -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to blink-dev+unsubscr...@chromium.org. To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAAozHLm7CR6EeL2KmBFyFpYT%3DNPXmTg4roLKV%3D7dRcCE%2BOoGwg%40mail.gmail.com.
