FINDING · DEPLOYMENT

After blocking all *.google.com subdomains on September 22, 2022, China's censor lifted the block specifically for FCM endpoints on October 1 while leaving other Google services (Docs, Groups, Sites) blocked through at least February 2023. This selective whitelist exception — made after only days of blocking — indicates the censor judged the collateral damage to apps relying on FCM to be unacceptable.

From 2023-xue-use — The Use of Push Notification in Censorship Circumvention · §5.1, Figure 5 · 2023 · Free and Open Communications on the Internet

Implications

Design circumvention transports around services with demonstrated collateral-damage immunity (e.g., FCM, APNS) rather than generic cloud infra; evidence that censors explicitly whitelist them provides a durable blocking-resistance argument.
Track censor whitelist behavior longitudinally — a service that survived one blocking event with a whitelist exception is empirically more resilient than one with no tested history.