Tahoe problems: how to revert to OS 15 Sequoia

It is not possible to downgrade the OS on an iPhone or iPad at all.

Downgrading macOS is not a simple matter. I agree with the advice above that you find solutions for your problems other than exercising the nuclear option.

Why don't you try actually explaining what's wrong instead of editorializing. We may be able to help you.

KiltedTim wrote:

It is not possible to downgrade the OS on an iPhone or iPad at all.

Downgrading macOS is not a simple matter. I agree with the advice above that you find solutions for your problems other than exercising the nuclear option.

Why don't you try actually explaining what's wrong instead of editorializing. We may be able to help you.

👍

neuroanatomist wrote:

The short version is that you’re better off finding solutions to your problems than downgrading. Not even sure you can downgrade iDevices to 18.

Judging by the complaint level here, Tahoe is no worse than Sequoia or Sonoma. Change is hard for some people. Personally, I’ve had no real issues with Tahoe despite upgrading on day one (instead of waiting for x.1 as I typically do). The worst ‘problem’ I had was with some iPhone icons randomly switching from dark to light mode at the wrong times, I survived that.

From what I have only read about

Once Apple issues an update of an exiting iOS and stops Signing the older version of iOS

That closes the doors for downgrading

If one extends this to iOS 18 of any version and iOS 26 is released

It would be reasonable to conclude, downgrading back to iOS 18 - the door would be closed

And Yes, I concur on your assistant of the macOS issue

🦉-53

The short version is that you’re better off finding solutions to your problems than downgrading. Not even sure you can downgrade iDevices to 18.

Judging by the complaint level here, Tahoe is no worse than Sequoia or Sonoma. Change is hard for some people. Personally, I’ve had no real issues with Tahoe despite upgrading on day one (instead of waiting for x.1 as I typically do). The worst ‘problem’ I had was with some iPhone icons randomly switching from dark to light mode at the wrong times, I survived that.

I have issues with stalling and password in Tahoe. I mistakenly changed to Tahoe when both Tahoe and Sequoia were in my Updates in System Settings. Five days in and no matter those who have no issues say, there are issues with the very obvious fact that my Macbook Pro is stalling when opening my Bills and viewing saved videos of my backyard. Definite as it gets. Also being asked for or told "incorrect password” on sitesI regularly use.

Right now my Water Bill is sitting there with the spinning sign of stalling.

I tried to revert by using my back up drive but it kept opening Tahoe. All attempts to open Time Machine to open and revert to previous OS Sequoia failed. Not satisfied with results, but I asked for it. Living with last version of Tahoe.

One issue that generally rears its head when doing OS upgrades is app compatibility.

One should always verify that their mission critical apps are 100% compatible with the new upgrade before doing the upgrade, i.e. Sequoia to Tahoe. The other thing overlooked is compatibility of any specialized hardware drivers with the newer OS.

Note: Manufacturer drivers for disk drives are never needed for USB drives and haven't been for years (even for Win10 or 11). They generally interfere with the ways macOS handles working with the drives. Initially they may seem okay but any update or upgrade can cause them to break things.

H. Lamar Thomas wrote:

...All attempts to open Time Machine to open and revert to previous OS Sequoia failed. Not satisfied with results, but I asked for it. Living with last version of Tahoe.

Time Machine has not backed up the OS for years now and only backs up user data and apps and their associated data.

Figural wrote:

I need to revert my four devices, Mac Mini (2025, M4), MacBook Air (2024 M3), iPhone 13, iPad Air, to the previous OS's mmediately before Tahoe (Sequoia). This is because Tahoe (26.1) is making both my desktop machine and laptop dysfunctional. Particular problems with Password Manager have forced me to switch to a third party app for security. 

Can someone point me to a reliable guide to doing this reversion, please? I'm not a techie but can follow instructions! In my personal circumstances I'm completely dependent on a reliable computer for many everyday things and with Tahoe a Mac isn't that right now. This is the worst computer experience I've had since the Great Windows NT4 Fiasco late last century turned me into a Mac (G4, OS9) user overnight.

I will be reporting what I'm seeing to Apple, and posting here, when I can but I'm still adding to the list :-(.

Any help would really be appreciated.

TIA.

Pauline

Respectfully, will Only Speak to Apple Computer using macOS

To get support regarding downgrading iOS devices, it is suggested asking in the appropriate iOS forums

Downgrade Apple Silicon computer

• User Risk Assessment: macOS Downgrade Procedure
• Before initiating any downgrade from macOS 26 (Tahoe) to an earlier version such as macOS Sequoia, assess the user’s tolerance for potential risks. The following checklist must be completed before proceeding.

Primary System Dependency

Determine whether the affected Mac is the user’s primary or only computer.

• If the user cannot function without this system for several days in the event of a failed downgrade, the risk level is high.
• The downgrade should be postponed or avoided until proper contingency measures are established.

Availability of a Secondary macOS System

Confirm that the user has access to another Apple computer currently running macOS 15 or macOS 26 (Tahoe).

• This secondary system must be capable of performing a Revive or Restore operation on the target Mac’s firmware if required.
• Lack of a secondary Mac significantly reduces the ability to recover from firmware corruption or boot failures.

Firmware Compatibility and Secure Enclave Risks

Be aware that upgrading to macOS 26 (Tahoe) likely includes a firmware update affecting the logic board and Secure Enclave Processor (SEP).

• Downgrading to an earlier version (e.g., Sequoia) may introduce firmware mismatch issues, leading to instability or loss of functionality.
• There have been at least three documented cases where downgrading from Tahoe to Sequoia resulted in Secure Enclave malfunctions, requiring full system restoration or hardware servicing.

Backup Integrity and Recovery Preparedness

Verify that the user has at least three complete backups created before the macOS 26 (Tahoe) upgrade.

Implement the 3-2-1 Backup Strategy:

• 3 total copies of essential data
• 2 different backup methods or storage media
• 1 copy stored offsite (for protection against natural or human-caused disasters)

Each backup should reside on a dedicated, single-purpose external drive.

For enhanced backup and cloning capabilities beyond Time Machine, refer to:

https://bombich.com

Recommendation Summary

If the user answers NO to any of the above questions:

Downgrading the Mac is not recommended.

Proceeding without proper contingency plans, verified backups, and recovery tools may result in:

• Data loss
• Firmware corruption
• Secure Enclave failure
• Complete system inoperability

Firstly, Time Machine Backup will only backup what is in your User Account ( home folder )

TM Backup does not contain and full and working copy of the Operating System

To roll back to macOS 15 from macOS 26 Tahoe is a risky business as previously outlined

This does not mean it is impossible, just not recommenced

And Yes, my colleague @woodmeister50 👍 has some very good points

woodmeister50 wrote:

H. Lamar Thomas wrote:

...All attempts to open Time Machine to open and revert to previous OS Sequoia failed. Not satisfied with results, but I asked for it. Living with last version of Tahoe.

Time Machine has not backed up the OS for years now and only backs up user data and apps and their associated data.

+ 1

🦉-53