* Chrome shipped support for Web Push Notifications using FCM Sender IDs M42 (March 2015), after which we added support for a standardized authentication path in M52 (July 2016). * We have been deprecating support for FCM Sender IDs since, adding console warnings and blocking the list of senders in 2019, and blocking all new subscription requests using sender IDs in 2020. Today we see <1000 unique senders still relying on Chrome to receive such messages in a 7-day window -- this is a tiny portion of full Web Push usage. * Following this prolonged deprecation path, we're now proceeding to remove support for Chrome to receive messages for subscriptions that were once created using FCM Sender IDs. Users who receive such messages will stop receiving them until they re-visit the sender's website, at which time it has the chance to renew the subscription. We unfortunately cannot automatically update such subscriptions. The roll-out will be done server-side.
This removes a long-deprecated, now barely-used proprietary addition in our Web Push Notifications implementation.