iOS 27: Safari ads bypass Wi-Fi ad blocker via cellular Connectivity Assist

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Level 1

31 points

iOS 27: Safari ads bypass Wi-Fi ad blocker via cellular Connectivity Assist

Since iOS 27, my iPhone and my iPad Pro (cellular model) show ads in Safari even though my home network blocks them with Pi-hole (a DNS ad blocker).

What I found:

- Pi-hole's log shows it blocked an ad domain at 10:37:05.

- A Safari Web Inspector web archive of the same page shows files from that same ad domain loaded at 10:37:05.

- Cellular data off = ads gone. Cellular data on = ads come back.

So when the Wi-Fi network blocks a request, iOS retries it over cellular, using the carrier's DNS. The phone is on Wi-Fi the whole time.

Apple's own support page for Connectivity Assist (support.apple.com/en-us/127686) lists ad blockers as a reason to turn it off. So this looks like the feature working as designed. But it means any DNS filter on the network (home ad blockers, parental controls, school or work filters) gets skipped silently on any device with cellular.

Workaround: turn off Connectivity Assist in BOTH places:

1. Settings > Wi-Fi > Connectivity Assist

2. Settings > Wi-Fi > tap (i) next to your network > Connectivity Assist

It also seems to keep the cellular radio busy. Others report battery drain and GBs of cell data used while on Wi-Fi (see the iOS 27 battery drain thread: discussions.apple.com/thread/256360287).

Has anyone else seen this? Is there a way to make iOS honor a network's blocks without turning the feature off?

iPhone 17 Pro, iOS 27

Posted on Oct 3, 2026 1:32 PM

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Answer 1

arun268

Level 1

20 points

Oct 12, 2026 8:30 PM in response to wilburmeinen

I discovered something interesting with my new iPhone. I run Pi-hole with Unbound on a raspberry pi5, and despite having a stable 1 Gbps connection with 6 ms latency, my iPhone was consistently loading blocked websites and ads.

Pi-hole was receiving DNS queries, both iPhones had identical DNS settings, and my other iPhone blocked everything correctly. Even Safari and Chrome behaved the same way.

The culprit? Apple’s Connectivity Assist. The moment I disabled it, Pi-hole blocking started working correctly.

My suspicion is that iOS may be silently bypassing my configured DNS filtering, potentially treating intentionally blocked domains as connectivity failures and using an alternative path.

I find it hard to believe this is simply about unreliable Wi-Fi when the connection is consistently fast and stable. It almost feels like deliberate behavior that undermines DNS-based ad blocking.

I can’t prove Apple’s intent, but the behavior is concerning. If I configure my own DNS server, my device should respect that choice instead of silently working around it.

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Answer 2

arun268

Level 1

20 points

Oct 13, 2026 6:22 AM in response to arun268

Update: Another potential bug with Connectivity Assist on iOS 27

I discovered another concerning behavior on my iPhone 18 Pro.

After manually disabling Connectivity Assist for my Wi-Fi network, turning Wi-Fi off and back on appears to automatically re-enable the feature, even when reconnecting to the exact same network.

This raises a separate concern beyond bypassing Pi-hole DNS filtering: iOS doesn’t appear to consistently preserve the user’s explicit network preference.

My Wi-Fi connection is performing at over 1 Gbps with 6 ms idle latency and 0% packet loss, so poor network performance is not an obvious explanation.

If a user explicitly disables Connectivity Assist, that preference should persist across Wi-Fi reconnections.

I’ll also check whether disabling Connectivity Assist in both the global Wi-Fi settings and individual network settings prevents it from re-enabling.

Has anyone else reproduced this behavior on iOS 27?

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Answer 3

wilburmeinen Author

Level 1

31 points

Oct 17, 2026 7:47 PM in response to arun268

This may bypass parental controls on a WiFi network.

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