iOS 27 re-enables Connectivity Assistance, bypassing DNS ad blockers
A setting turned back on during the update to iOS 27 pushes iPhones onto mobile data and lets ads through; a few taps switch it off.
Apple has re-enabled Connectivity Assistance on iPhones updated to iOS 27, and the setting is disrupting ad blockers that filter DNS locally.
The option lets a phone use 4G or 5G alongside Wi-Fi when the Wi-Fi connection appears to have problems. A local DNS filter stops some content from loading, which the system reads as a network fault, so the iPhone falls back to mobile data, where pages arrive without the filter, ads included.
The behaviour is intentional: the explanation attached to the setting tells people who use an ad blocker that they may want to turn it off. The bug is elsewhere. The setting was automatically switched back on during the move from iOS 26 to iOS 27, as users on Reddit noticed.
Owners can disable it for every network under Settings, Wi-Fi, Connectivity Assistance, or for a single network by tapping the “i” beside it. Filtering through an external DNS service and a configuration profile should keep working, since it covers all connections.
