Ready for Trial: Permission-Policy: unload
Fergal Daly
Contact emails
fer...@chromium.com
Explainer
https://github.com/fergald/docs/blob/master/explainers/permissions-policy-unload.md
Specification
https://github.com/whatwg/html/pull/7915
Summary
This feature allows pages to disable the running of unload event handlers. The goal is to : - allow sites that have removed all unload handlers to ensure they do not accidentally add new ones - allow sites to remove unload handlers when updating the code is infeasible Unload event handlers are problematic for various reasons and prevent use of BFCache on Desktop (see https://web.dev/bfcache/#never-use-the-unload-event).
Blink component
Blink>PermissionsAPI
TAG review
https://github.com/w3ctag/design-reviews/issues/738
TAG review status
Pending
Risks
Interoperability and Compatibility
3rd-party frames that rely on unload may not work as expected when navigating away. This is solvable by the frame authors by use of alternatives to unload and is unlikely to impact users. See detailed discussion.
https://github.com/fergald/docs/blob/master/explainers/permissions-policy-unload.md#concerns-about-giving-embedders-control-over-the-nonexecution-of-iframe-code
Gecko: Negative (https://github.com/w3c/webappsec-permissions-policy/issues/444#issuecomment-1047829132) FF objects to this similar to sync-xhr and document-domain providing a way to cause cross-origin interference with script. Explainer addresses this (https://github.com/fergald/docs/blob/master/explainers/permissions-policy-unload.md#concerns-about-giving-embedders-control-over-the-nonexecution-of-iframe-code) This is not a formal FF position, we will request a formal position soon.
WebKit: No signal
Web developers: Positive Private discussions with devs are positive. Sites that have made efforts to remove all unload handlers want to use this to prevent accidental returns. Also some providers of 3rd-party iframes which have content outside of their control (e.g. ad network) want to guarantee themselves to be unload-free. https://github.com/w3c/webappsec-permissions-policy/issues/444#issuecomment-1130401722 Also positive feedback about using this to deny unload as a source of security problems. https://github.com/w3c/webappsec-permissions-policy/issues/444#issuecomment-1222973324
Other signals:
3rd-party frames that rely on unload may not work as expected when navigating away. This is solvable by the frame authors by use of alternatives to unload and is unlikely to impact users. See detailed discussion. https://github.com/fergald/docs/blob/master/explainers/permissions-policy-unload.md#concerns-about-giving-embedders-control-over-the-nonexecution-of-iframe-code
Gecko: Negative (https://github.com/w3c/webappsec-permissions-policy/issues/444#issuecomment-1047829132) FF objects to this similar to sync-xhr and document-domain providing a way to cause cross-origin interference with script. Explainer addresses this (https://github.com/fergald/docs/blob/master/explainers/permissions-policy-unload.md#concerns-about-giving-embedders-control-over-the-nonexecution-of-iframe-code) This is not a formal FF position, we will request a formal position soon.
WebKit: No signal
Web developers: Positive Private discussions with devs are positive. Sites that have made efforts to remove all unload handlers want to use this to prevent accidental returns. Also some providers of 3rd-party iframes which have content outside of their control (e.g. ad network) want to guarantee themselves to be unload-free. https://github.com/w3c/webappsec-permissions-policy/issues/444#issuecomment-1130401722 Also positive feedback about using this to deny unload as a source of security problems. https://github.com/w3c/webappsec-permissions-policy/issues/444#issuecomment-1222973324
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?
none known
Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?
none known
Goals for experimentation
- Validate that this allows sites using it to improve their BFCache hit rate
Ongoing technical constraints
Debuggability
N/A
Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?
Yes
Is this feature fully tested by web-platform-tests?
Yes
Flag name
chrome://flags#enable-experimental-web-platform-features
--enable-features=PermissionsPolicyUnload
Requires code in //chrome?
False
Tracking bug
https://crbug.com/1324111
Launch bug
https://crbug.com/1357927#c16
Estimated milestones
| DevTrial on desktop | 107 |
| DevTrial on Android | 107 |