iPhone system data filling up device after iOS 26 update

I know many will probably disagree. But such a big update from iOS 18 to iOS 26 should be done as a "clean" update. I personally don't see the point of iCloud Backup anymore. All your photos, files, contacts, etc. are continuously backed up, and it's automatically downloaded when you sign in with your Apple Account. Apps can just be downloaded again in the App Store.

The only advantage I can see is that the wallpaper and apps are in the same place on the screen after you restore from an iCloud Backup. But often you have to sign in to all the apps again anyway.

Here's how I do it. I make sure iCloud is up to date, so that all photos, files, etc. are synchronized. After that, I sign out of my Apple Account. Then I choose Erase All Content and Settings. When the phone is restored to factory settings, I connect it to my Mac (can also be done from PC, iTunes), and then I do a restore, where everything is wiped again and the latest full update is downloaded and installed.

Once that's done, I set up the phone as new without a backup. Then I sign in with my Apple Account, so that photos, contacts, files, calendar, etc. are synchronized back to the phone. Then I download the apps I use again from the App Store, and set them up one by one.

That way you get a clean start. By using the backup, you drag everything, including your problems, onto a new software - or a new iPhone. It can be time-consuming. But in return, you have an iPhone that just works, and you get rid of all the system data that has accumulated.

I had this problem too with the upgrade on my iPhone 12 Pro Max.

One of the thing that seems have solved it is to disable the automatic download of new system updates (General-Software Update) because iOS was reserving space for them (almost 12 GB).

"iPhone system data filling up device after iOS 26 update: [...]I ended up backing up the device, wiping it, and restoring it from backup and I noticed that i had about 60GB of space free. [...]Can anyone give me some advice here?"

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To the OP and All those Affected:

A. Properly Clearing System Data After an Update:

The erasure between the backup and then restore may be the issue here, as it is not a required step In this process. Here is my User Tip on how to clear of the System Data: How to Clear "System Data" in your iPhone's Storage: - User Tip

B. Report this Bug to Apple:

Do your Part: These are user-to-user forums. Apple rarely reads these forums on their own time as it is. So, provide Apple with feedback on this.  Apple wont get back to you directly, but the more they hear of this, the more they will know what is going on, and what needs to be fixed.

To Provide Feedback:

1. Go Here: Feedback - iPhone - Apple
2. Select: "Bug Report" for the "Feedback Type"
3. Comment: when this all began, and how you have troubleshot this thus far. Include the URL of this thread.
4. Proceed form there as necessary

Update: Apple Support was great and walked me through iPhone restore. Half the phone is now clear. You have to connect to Mac, put phone in restore mode (hold down power while phone is connected to Mac), re-install the OS, then restore from latest cloud backup. Hopefully this will do the trick - will watch it over the next couple weeks. Apple reports that 13GB or so should be typical for system data on iPhone.

“[…]But since iOS 26, iPhone keeps Running: out of Memory and the System Data keeps Ballooning, After Restoring Multiple Times, and Multiple Calls to Apple. if anyone gets a Resolution, Please Post it.”

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Clearing System Data in a Loop After Update:

A. Use my User Tip:: How to Clear "System Data" in your iPhone's Storage: - User Tip

B. Reset to Factory Settings:

If still getting this issue, you may need you backup your iPhone to a computer, and then reset it to Factory Settings. Look into taking a few screenshots, and then email them to yourself, as a way to remember what when where, and how things were configured. Enabling Items in iCloud (ie Photos and Messages), you can back them up, if you have free storage to do so.

I have the exact same problem with my iPhone 15 Pro 256GB version. I had more than 130GB of free space but after updating to iOS26 the system data started filling up any empty space.

I cant even receive emails now!

Apple please fix this as it must be some kind of bug.

Same problem for me. It’s killing my iPhone 15 Pro. 64GB of system data and even if I delete apps it keeps filling the space. Wiped and restored, plenty of space, then 2 weeks later it’s back up to full. Apple please fix this ASAP. My phone is becoming useless. And, please provide users more control and visibility over system data so we can see what is going on.

Yep. Back to full. Disappointed. Like you I will have to do this every two weeks. Productivity killer so I hope it get fixed soon. It’s brutal. iOS 26.1 Beta 4 is available but I haven’t tried it. Need to wipe my phone again to make space.

[HELP HELP HELP]

I am Having the Same Issue.

iPhone 15 Pro Max with 90GB Free on iOS 18.7, with no issues at all.

But since iOS 26, iPhone keeps Running out of Memory and the System Data keeps Ballooning,

After Restoring Multiple Times, and Multiple Calls to Apple.

if anyone gets a Resolution, Please Post it.

Thanks for the write up. Looks like that's the plan.

Was the Issue Solved ?