1. Confirm the leak
On home Wi-Fi, ads load that your DNS usually blocks, and the Pi-hole/NextDNS log shows no query. Cellular DNS is answering instead. r/pihole and r/nextdns reported this from beta through 27.0; the upgrade can even re-enable the switch.
2. Flip the master switch
- Settings → Wi-Fi.
- Connectivity Assist → Off.
- Stay on Wi-Fi and reload a site that was leaking ads.
3. Per-network control (if you want Assist away from home)
iOS 27 also has a per-SSID control: Settings → Wi-Fi → (your network) → Use Cellular Data with Wi-Fi. Leave the master switch on, turn that off for home. Use Assist on coffee-shop Wi-Fi only.
4. If you use a NextDNS profile that excludes home SSID
r/nextdns: excluding home Wi-Fi from the profile plus Connectivity Assist means cellular DNS (unfiltered) handles the “failed” ad lookups. Either stop excluding the SSID or disable Assist on that network.
Do not do these
- A VPN that only starts off home Wi-Fi will not save you: the phone still thinks it is on Wi-Fi.
- DoH/DoT configuration profiles are more resistant than plain router DNS; Assist can still bypass router-only Pi-hole.
Questions this page actually answers
Is this the same as old Wi-Fi Assist?
Same family, new name, more aggressive. It can run without switching the status-bar icon to cellular.
Will this increase battery use if I leave it on?
Cellular fallback uses radio time. The usual complaint is ads and DNS leaks, not battery, but both can happen.
Next useful pages
Sources
- Apple Support: How to download iOS 26
- Apple Support: Back up your iPhone
- Apple iOS 27 compatibility list
Prepared by the iPhone Update Editorial Desk. Independent technical reference. Not affiliated with Apple Inc.