Be aware: Connectivity Assist changes how your phone networking works

[bigboy29]

Settings > Wi-Fi > Connectivity Assist

This seems to be a new version of what used to be "Wi-Fi Assist" under Cellular. But it seems to be much more aggressively used in iOS 27. It essentially seamlessly mixes your Wi-Fi data with cellular data (unknown under which conditions).

You can then get situations like the following:

• If you use some sort of ad blocking on your home Wi-Fi, your phone might bypass local network name resolution. Any DNS sinkhole like AD Guard or Pihole might get bypassed all of a sudden even though phone is on Wi-Fi.
• If you have a VPN client that starts when you drop from your home or work Wi-Fi (for example, Wireguard) - the phone might use Cellular data but because you are still connected to Wi-Fi, VPN never activates.
• If you are on a limited data cellular plan, your phone might burn your Cellular data allocation even though you are on Wi-Fi.

I have seen two of the above; I feel like it is not a bad feature for situations where you have very large / unlimited cell data plan and possibly sketchy Wi-Fi connectivity, but there are definitely downsides! So be aware.

I turned it off.

 

[archvile]

Unfortunately the cellular data usage and call time stats seems to be borked in 27 as they both show all zeroes on my phone even though I have used plenty of both in the past few days, so I can't see how much of my data is actually routing through the Connectivity Assist feature

 

[adrianlondon]

I just checked mine, and I've used 9MB since I reset data stats at the beginning of the month.

I like the fact it tells you how much data it's used underneath the setting.

I'm going to keep an eye on it. I have unlimited data unless I'm roaming. It's a pity that this setting isn't Wi-Fi network dependent.

 

[VSMacOne]

For unlimited data users the feature is much improved over previous years. I appreciate the smoother transition between cellular and WiFi.