iOS 9 — How did the launch really go?

Apple's iOS 9 update was released on September 16, 2015, and its adoption rate exceeded expectations. Analyzing user agent strings of requests passing through the CloudFlare network revealed a spike in usage immediately after launch and another when Europe woke up. As of September 21st, iOS 9 adoption was around 30-35% relative to iOS 8 on the CloudFlare network. The update also contributed to an increase in IPv6 requests due to its requirement for all iOS apps running on iOS 9.0+.