You can return the macOS version, but the operation is complicated and risky. 1. Use Time Machine to roll back the system: the premise is that the backup has been turned on and the complete mirror has been made. The entire system will be restored to a certain time point during operation, resulting in the loss of subsequent new data; 2. Manually reinstall the old version of macOS: you need to prepare to start the USB drive, erase the system disk and install the old version. The process is cumbersome and will clear all current data; 3. Data backup and precautions: No matter whether you do this, you must back up the data in advance, pay attention to the limitations of the system version of different models, and it will be difficult to downgrade after Apple officially stops signing the old version, and M series chip models are particularly limited.

After updating macOS, it is possible to find that the system card is changed, the driver is incompatible, or some software cannot run normally, which is a problem that many people will encounter. At this time, many people will wonder: Can you return the system version? The answer is - Yes, but not simple.

1. Use Time Machine to roll back the system version

If you have enabled Time Machine and have done a full backup, this is the most direct way to fall back. However, it should be noted that this method is actually to restore the entire system to its pre-update state, not just to simply downgrade the system version.

The operation steps are roughly as follows:

• Connect your Time Machine backup disk.
• Restart the Mac and immediately press and hold Command R to enter recovery mode when powering on.
• Select "Restore from Time Machine Backup" in the tool interface.
• Follow the prompts to select a backup point that was earlier than you upgraded to restore.

It should be noted that this will restore the files, settings and applications of your entire system to the state of that point in time, which is equivalent to "rewinding time". If you add a lot of new data during this period, these will be overwritten.

2. Manually reinstall the old version of macOS to achieve downgrade

If there is no Time Machine backup, you can also downgrade by manually installing the older version of macOS. But this usually means you need to clear the system disk and reinstall the old version, so be mentally prepared: this process will clear all current data.

Specific practices include:

• Prepare a USB drive to create a boot disk (at least 16GB).
• Use another Mac to download the corresponding version of macOS installer (for example, if you want to install macOS Big Sur, you need to download the corresponding installation package).
• Format the USB drive to "Mac OS Extension (Logistic)" with the name to "Untitled" or other suitable name.
• Use terminal commands to create a bootable installation media, for example, using sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled .
• After inserting the boot disk, restart the target Mac, enter recovery mode (Command R), and select Disk Utility to erase the built-in hard disk.
• Next, you can install the old version of macOS from the boot disk.

This method is suitable for users with certain hands-on ability, and the old version of the installation package must be prepared in advance. Not all versions can be found on the App Store.

3. Data backup and precautions

No matter which method, data security is always the first priority. Especially the second method is basically the rhythm of "reinstalling the system". Not doing data backup is equivalent to causing trouble.

Some key reminders:

• Before starting any operation, make sure that important information has been backed up to an external hard drive or cloud service.
• Different models of Mac support for system versions is different. For example, the M1 chip model cannot install Catalina and earlier versions.
• Apple's official official will generally stop signing verification of the old version shortly after the new version is released. Once this time window is passed, it will be difficult for you to successfully downgrade.

In addition, Apple has increasingly restricted system downgrades, especially on Macs with M-series chips. Many old methods may no longer apply.

Basically that's it. If you just accidentally upgrade the system and have a full backup, there is still a chance to return it; but if it has been a while or has not prepared, you have to weigh whether it is worth it.

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