When you encounter the prompt "macOS installer is corrupted and cannot be used", the problem is usually not that the installation package itself is corrupted, but that there is an error in the verification mechanism or storage method. 1. Re-download the macOS installer, and priority is obtained from Apple's official channels to ensure integrity; 2. Turn off the installation verification in SIP, and after entering recovery mode, enter the csrutil disable command to temporarily close the verification and restart the installation; 3. Check whether the USB boot disk is made correctly, it is recommended to use the createinstallmedia command and ensure that the USB disk format is Mac OS extension; 4. Correct the time and date settings, adjust the time through the date command in recovery mode to avoid misjudging the certificate expiration. After completing the above steps, most cases can solve this problem.

When you encounter the prompt that "macOS installer is corrupt and cannot be used", many people will think that there is a problem with the downloaded image file. In fact, this situation can be solved in a few simple steps most of the time. The problem is usually not in the installation package itself, but in some minor problems with the verification mechanism or storage method.

1. Re-download macOS installer

Once the installer provided by Apple is damaged, the most direct and effective way is to re-download it. Sometimes network fluctuations or interruptions can lead to incomplete downloads.

• Open "App Store" and search for the macOS version you need (such as Ventura, Monterey, etc.)
• Delete the currently existing installer (go to "Applications" > Right-click to delete)
• Re-download to ensure that the network is not interrupted during the download process

If you are getting the installation package from a third-party website (such as some technical forums), there is indeed a possibility of file corruption, and it is recommended to obtain it from Apple's official channels first.

2. Turn off installation verification in System Integrity Protection (SIP)

macOS will perform signature verification on the installer for security reasons. If this verification fails, it will prompt "The installer is corrupted". You can try to temporarily turn off this verification function:

• After shutting down, press and hold the power button to enter "Startup Options"
• Press and hold Command R to enter recovery mode
• Open Terminal
• Enter the command: csrutil disable
• After restarting, try running the installer

Note: After completing the installation, remember to restart SIP and enter csrutil enable for more security.

3. Check whether the USB boot disk is made correctly

If you are using a USB flash drive to install macOS, it may also be because the writing method is incorrect, which makes the system think that the installation media is untrusted.

• Using the "terminal" command to create a startup disk is more reliable (for example, createinstallmedia command)
• Make sure the USB format is Mac OS extension (log-style)
• Don't rush to pull the disk after writing, "release" first and then pull it out.

Although some graphical tools (such as BalenaEtcher) are convenient, they may not be fully compatible with macOS's signature mechanism. It is recommended to use the methods officially supported by Apple.

4. Time and date setting errors may also cause this problem

You may find it strange, but the macOS installer verifies system time. If your time is set incorrectly (such as the year is wrong), it will misjudgment that the certificate has expired, thus reporting an error "installer is corrupted".

• Open Terminal in Recovery Mode
• Enter the command to view the current time: date
• If the time is obviously wrong, manually adjust:
  • date MMDDhhmmYYYY (for example, date 050112002024 means 12:00 on May 1, 2024)

Try running the installer after adjusting the time. Although this problem is rare, it may indeed occur when old equipment or motherboard batteries are out of power.

Basically, these common causes and solutions are all about them. In most cases, you can do it by re-downloading the installation program or adjusting the system settings, and there is no need for too complicated operations. However, it should be noted that Apple's verification mechanism for installing programs is becoming increasingly strict, and it is trying to keep the time and system environment accurate as much as possible, which can avoid many unnecessary troubles.

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