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.

EDIT: With DB4, there is now also a setting under individual Wi-Fi network that is called "Use Cellular Data with Wi-Fi" and this settings seems to have no effect (yet). Having Connectivity Assist enabled makes individual Wi-Fi network use Cellular no matter if you toggle the specific Wi-Fi toggle off or not. Hopefully in a later beta...

 

[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.

 

[poocat]

I am curious if this feature is disabling 1Blocker? I see ads in apps that I usually don’t. Also there’s no VPN settings panel or is that because I only have one installed?

 

[chrfr]

I am curious if this feature is disabling 1Blocker? I see ads in apps that I usually don’t. Also there’s no VPN settings panel or is that because I only have one installed?

The VPN settings are where they've always been, so perhaps you need to open 1Blocker and reinstall the in-app blocker.

 

[poocat]

The VPN settings are where they've always been, so perhaps you need to open 1Blocker and reinstall the in-app blocker.

I've opened 1blocker, it's up, the VPN says connected (which is normal) and I've re-started the phone. I'll definitely try re-installing, good idea.
Otherwise guessing it's a bug in one or the other.
Also I don't have VPN settings - here's what it looks like and why I thought it was odd. VPN used to have an arrow to settings. Maybe because I used to have 2 installed?

 

[poocat]

Further testing confirms it's Cell assist:
1. Reinstall 1blocker same result
2. Open Bloomberg (app w/ ads) while on wifi - ads load slower than content
3. Current cell assist data is 570 mb, up after opening Bloomberg
4. Quit Bloomberg
5. Turn off cell assist
6. Re-open bloomberg
7. No ads.

Thus some learnings:
1. Cell assist ignores VPN connections
2. Cell assist enables ad tracking!
Fun times.

Also, VPN config is under General > VPN & Device Management, and only shows an > in Settings top level if 2 are installed.

 

[southerndoc]

I disabled it. Definitely do not want this as I try to send as much traffic as possible through my home VPN when I'm away from home.

 

[poocat]

Further testing confirms it's Cell assist:
1. Reinstall 1blocker same result
2. Open Bloomberg (app w/ ads) while on wifi - ads load slower than content
3. Current cell assist data is 570 mb, up after opening Bloomberg
4. Quit Bloomberg
5. Turn off cell assist
6. Re-open bloomberg
7. No ads.

Thus some learnings:
1. Cell assist ignores VPN connections
2. Cell assist enables ad tracking!
Fun times.

Also, VPN config is under General > VPN & Device Management, and only shows an > in Settings top level if 2 are installed.

Following up here, I've submitted feedback 20261525630 for this, with full logging/repro steps/video/etc.
Would welcome further testing/submission.