How to Fix Slow Cellular Data on iPhone 12 Pro after iOS 18 update?

I have the same issue. I have a new iPhone 16 Pro Max and I'm on IOS 18.1 Beta 5. My phone shows that I'm on the 5G ultra wide network, but my downloads are abysmal - typically under 5Mbs. WIFI is fine, but cellular (both at home and at work) are terribly slow, so slow that I cannot update Apps from the App Store. I spoke with my carrier (Visible) and they tried a few things, but nothing has helped. I have toggled Airplane mode, Reset Network Settings, rebooted several times. The last suggestion from Visible was a factory reset. I might be doing that tonight.

Same issue with iPhone 14 pro max. No carrier settings updates, full bar signal strength, connection speed is pretty awful. Tried resetting usage statistics, restarting the phone (several times), disabled e-sim, no of this worked. It's a very poor experience trying to use mobile data connection.

I am also suffering extremely slow speeds since the "upgrade". I'm with MooseMobile which I believe uses the Optus network. I used the Speedtest app (Ookla) and I got this:

I usually get > 100 Mbps. A stark difference.

Very frustrating. I think I'll book in with Apple to see what they say.

solved for me.

1) Go to settings

2) go to general

3) go to reset

4) reset network settings ( it won't affect your data app passwords anything just )

and then connect dara or wifi again

I have the same issue.

I have a 13 Pro and am on the KPN network in the Netherlands.

The mobile data speeds are so laughably slow. Google’s Internet speed test literally shows me 0.04 MB/s.

I have tried resetting my network settings / restarting my phone multiple times / turning off/on airplane mode. Nothing seems to work.

I use iPhone 12 Pro Max and recently updated to iOS18 and the connectivity was so so so slow. Unitill I found the solution here. The above screenshot is before the Network reset was done. And the the speed increased after network reset. My issue is solved.

One possibility to check. Open safari and see how many internet browser windows are open in the background. If there are 30 or 40 or more, it may be trying to refresh them constantly and slowing things down. Should slow wifi down also though so not a complete solution, but something to try.

FWIW, I'm not having any problems with my iPhone 12 Pro with iOS 18 and I don't have anywhere near that reported cell strength. Who is your cell carrier? Are you running any sort of VPN on your iPhone?

If you're experiencing slow cellular data on your iPhone 12 Pro after the iOS 18 update, despite full 5G bars, try these steps: update carrier settings, toggle Airplane mode, and check for any pending iOS updates. If the issue persists, contact your carrier for network troubleshooting or visit an Apple store for further diagnostics. Several users have reported similar problems after the update.

Same here. Resetting network settings didn't work, a complete erase and re-setup was necessary. That appears to also have fixed quite a bit of other issues, like UI lag and erratic touchscreen behavior, so I won't be restoring from backup. iPhone 12 mini.

iPhone 15 pro max - updated on Dec 2nd. Experiencing extremely slow network speed - under 1 mbps. Seeing that some of you had this issue in September made me very sad. I understand that sometimes updates can go wrong, but this is unacceptable. Resetting the network settings didn’t fix the issue.

I have an update. I got ahold of the carrier and explained what happened. Not sure what they did, but after 5-6 minutes of wait they told me to put the phone in a plane mode for 1 minute and then test the speed. Whatever they did worked and I have a good internet speed ever since.

if you chose to do a network reset, keep in mind that all of your WiFi passwords will be erased. Considering it didn’t fix my issues as I now have to get all of the WiFi passwords that I’ve been keeping for years.

[Edited by Moderator]

Sorry, other than possibly doing a factory reset of your iPhone:

How to factory reset your iPhone, iPad, or iPod touch - Apple Support

I can't think of anything else to try. Perhaps someone else here will be able to think of somethng to suggest.

Regards.

I'm on a 16 Pro Max with iOS 18.0 and have also been experiencing this. I'm on Singtel in Singapore.