Can I downgrade from iOS 26 to iOS 18 using a backup?

No. Backups do not contain the iOS at all. So you cannot restore the backup made on iOS 18 to an iPhone which is on iOS 26 and in any way go back to iOS 18. Simply said, downgrading has never been supported. Also, this is a user to user only forum. Apple isn't here and doesn't read this forum for user feedback.

The vast majority of people aren't having heating issues, nor does the iOS make the battery lose capacity. Batteries are consumable parts and with every full cycle battery charge, regardless of the iOS, the battery will lost some of its health. This is normal and cannot be stopped. What is your current Battery Health? Settings > Battery > Battery Health.

When you say your phone is overheating, are you seeing a red thermometer on your screen with a warning the phone can't be used until it cools down? If no, your phone isn't overheating.

Often after an iOS update, Force Restarting helps and it's something I do after EVERY iOS update. Do you do this --> Force restart iPhone - Apple Support

If you aren't pleased with Liquid Glass, I wrote this to help people, so see if anything here helps you --> Liquid Glass - Love It Or Hate It - It's … - Apple Community

i have backup of a ios 18, can i downgrade my 26 ios somehow?

No, because backups do not store the iOS version.....they only store the data on the iPhone.

And, Apple has never supported downgrading the iOS version once a new update has been officially released.

MicahTechDev wrote:

Apple should give users the choice to install older iOS is they want to, at their own risk. They already do this for Mac devices. You can downgrade a Mac via ipsw as well as a usb installer, officially, no shady tools needed.

This is a user to user only forum. Telling only other users what you think Apple should do, won't get you anywhere. Apple has NEVER supported downgrading iOS. They likely NEVER will as it would mean removing features and require maintaining multiple versions of iOS. Android doesn't officially support downgrading either.

But you are welcome to tell Apple what you think they should do here --> Feedback - iPhone - Apple

Apple will usually keep a signed previous version available for a few days after a new version is released......but you have to act very quickly.

Now.....let's say that you opt to install a beta version of the next iOS version. You can downgrade back to the current officially released iOS version during the beta period. It's not as easy as it sounds and there are drawbacks to doing this of course.

In addition, Apple strongly recommends that you only install beta software on a "spare" phone.....very good advice that way too many users ignore and later regret not following.

But, once a new iOS version is officially released, you only have a day or two to "go back".

If the battery is overheating, the battery needs to be checked and tested (and replaced).

Make an appointment at the Apple Store / Genius Bar or authorized Apple service shop. You can find a list of authorized shops in your area using this link:

Find Locations- Apple

Dumme_taube wrote:

i wish apple returned signing to ios 18 at least for a day.

I believe that iOS 18 updates may still be available for iPhones that

• Are compatible with iOS 26
• Have not yet updated to iOS 26

after a period during which Apple pulled all such updates.

This renewed availability is very unusual, but still doesn't get you the ability to downgrade iOS.

You're welcome to send Apple feedback at https://apple.com/feedback

MicahTechDev wrote:

I’m aware that it’s user only, I’m just spreading the word as I’ve already left feedback about this and they don’t really seem to care.

Also, it doesn’t not require them any extra maintenance actually, they already maintain older iOS versions, they just keep the updates exclusive to older phone models.

I’ve researched the topic heavily, and trust me when I say allowing iOS downgrades is something they can easily do, but choose not to, due to some skewed philosophy.

Ha! Having worked on operating systems internals and support, an operating system downgrade is an immense development and testing effort for the vendor, and for the third-party vendors. Way more support, too.

This unless it’s a nuke-and-pave reset-and-reinstall “downgrade”.

A nuke-and-pave is still more testing particularly around older and newer firmware working with older iOS and iPadOS versions, the ever-popular “fun” that is code signing and that all now with mixed-era certificates involved.

This iOS and iPadOS downgrade is inherently also a path for persistence and exploitation by malware and spyware and such.

As for iOS 26 and iPadOS 26 and Liquid Glass, the aforementioned love-it-or-hate-it article is a place to start. That got me to where I could ignore most of Liquid Glass and its shenanigans, and could read most of what it displayed. The macOS 26 user interface still being a work in progress (locally), however. Did get macOS into something all too reminiscent of X11 Motif / CDE, where it became much more legible.

TL;DR: Log your downgrade-request feedback with Apple, and hold off any further upgrades pending your own local testing, and whatever “27” eventually looks like.

when i was using ios 18, and had 217 cycle counts of charging i still had 100% of capacity,

Apple Support documents indicate that the battery in your iPhone is designed to go up to 1,000 Charge Cycles before it reaches 80% Maximum Capacity under ideal conditions.

That works out to about a 1% decline for every 50 charge cycles. If your battery was still at 100% after 200 Charge Cycles......you were very lucky that your battery was really at about 103-104% when it was new. But, Apple would have still displayed that as 100% Maximum Capacity. So, after 200 Charge Cycles, your battery displayed 100% Maximum Capacity.

Now your battery has returned to normal and you should expect about a 1% decline for every 50 Charge Cycles.

Keep in mind that Apple always "rounds down" the battery numbers by dropping any tenths of a percent. For example a battery that reads 96% might really be at 96.9%....or....it might be at 96.1%.

Let us know that the technician says when the check your battery.

Hi, iOS 26 and Liquid Glass are simply the design Apple has chosen to go with, for now. The iPhone User Interface has had several major redesigns in its near 20 year history. The last major redesign was iOS 7, back in 2014. We all somehow managed to get through them all. 

You may want to review the information in the article I linked to below. It explains the adjustments you can make to mitigate the effects of Liquid Glass that you’re experiencing. 

Liquid Glass - Love It Or Hate It - It's … - Apple Community

Apple’s installed user base is over 1.5 billion users. Making a single user interface perfectly compatible for every user is literally impossible. Apple will make changes (or not make changes) based partially on the feedback they receive through their official channel, linked below and good luck.

Product Feedback - Apple

I should also note that this past week Apple released details at WWDC on iOS 27 and many user suggestions have been incorporated into the tweaked design. Many icons have been updated and there will be a slider to adjust the Liquid Glass effect. iOS 27 is expected to be released publicly in September, about 3 months. A public beta will be available in July or August.

“my current capacity is 95, but when i was using ios 18, and had 217 cycle counts of charging i still had 100% of capacity,”

So it wasn’t reading properly before and now it is.

Okay.

“because i’m very gentle with all of my phones and pc, and never overcharged them”

You cannot overcharge them.

“also there was no battery draining”

Yeah there was. Your phone was not reading the battery correctly. If there was no battery draining, why plug it in?

I agree. I’ve been so upset with this redesign on so many levels. And I never complain but I’m just so frustrated I’m actually considering leaving the ecosystem. The moving of a search bar, the cartoonish designs on some of the icons. I could go on. This is the worst design I’ve ever encountered in sorry to say. Apple appears to be losing their way.

This is the worst design I’ve ever encountered in sorry to say.

To keep things in perspective.......we heard that same comment over and over again......from users who were having problems when iOS 18 was introduced.

We may hear similar comments this fall when the next iOS version is released. Guess we'll have to wait and see.