Why Did iPhone Update Automatically?

No one can answer your question here. We haven't seen what you actually had in settings. There are two places one can stop automatic updates. One for Apps and one for iOS updates. The way iOS updates work is if turn off automatic updates and never install a minor point update, the setting won't be changed. But if you for example, updated from iOS 18.7.1 to iOS 18.7.2, the switch for Automatic Updates is then turned back on and you'd have to go back in and turn it off again.

My guess is you has this one set to not update automatically How to manually update apps from the App Store - Apple Support instead of Update your iPhone or iPad - Apple Support

Do you recall manually updating your phone earlier this month to iOS 18.7.2? I believe the update became available on Nov 5.

If you did, that turned auto updates back on, likely or possibly without you noticing it at the time. So, when your phone saw iOS 26 as an available update, it installed the iOS 26 software.

The bottom line.....if you have auto updates turned off....and even if you manually update the phone.....auto updates are turned back on. You have to manually turn auto updates back off again.

Now, I am confused.

Your screenshot indicates that iOS 26.1 was downloaded......but it was not installed.

Were you thinking that your phone was updated? It wasn't.

Bob Timmons wrote:

Now, I am confused.

Your screenshot indicates that iOS 26.1 was downloaded......but it was not installed.

Were you thinking that your phone was updated? It wasn't.

As my post above yours indicates, that makes two of us who are confused. But I don't think it us who are confused.

This won't help, but my old iPhone 11 Pro which was set to Automatic Updates Off is still running iOS 18.

Sorry, I don't have the perfect answer, but if other users had their phone(s) set for Automatic Updates Off and iOS 26 was installed anyway, this site would be totally flooded with posts on the exact same issue. It's not. I spend about 10 minutes searching for similar reports and found none.

Plenty of other people manage to stay on iOS18, you must have overlooked some setting.

This is not the complaints department, try here https://apple.com/feedback

KatieOConnell wrote:

Thank you for your time.

OK......so the update downloaded, but according to your screenshot, it hasn't actually been installed on your iPhone. If you don't want it, you can remove the download. You can open Settings > General > iPhone Storage, look for the update and remove it.

Your title and question were actually incorrect. Your phone didn't update. But the update package was downloaded and can be installed to complete the update to iOS 26.1

KatieOConnell wrote:

Your response is not helpful. This wasn't intended as a complaint, just looking for some sort of explanation.

Maybe if you had offered the screenshot that showed, as others have said, it was not installed.

1. Go to Settings > General > iphone Storage.
2. Find the update in the list of apps.
3. Tap the update, then tap Delete Update.