To install an older version of OS X on a Mac, you must:

• Confirm your Mac meets the system requirements for earlier versions of OS X
• Locate and download a macOS installer file for the specific version you're targeting (it may come as a .dmg file)
• Prepare a bootable USB drive
• Boot your Mac using the installation disc or drive
• Ready your Mac for installation if needed
• Proceed with the installation by following the on-screen instructions

Check if your Mac supports the older macOS version

In general, running an older macOS version should be feasible. Issues typically arise when trying to run newer macOS versions on outdated Macs. Apple discontinues support for older models that can't efficiently handle new OS releases. While there are workarounds, they often result in reduced performance.

Steps to verify compatibility between your Mac and a specific OS X version:

1. Click the I logo located in the top left corner of macOS.
2. Choose About This Mac.
3. The Overview section displays your Mac’s model name and release year.
4. Refer to Apple's technical specifications pages for the macOS version you plan to install.

If your Mac is listed among the supported models, you should be able to downgrade to that version of macOS.

Finding and downloading an older macOS version

After confirming compatibility with a particular OS X version, the next step is to download the installer. Some recent macOS installers can be found directly in the App Store.

Use these links to access them quickly:

• macOS Catalina
• macOS Mojave
• macOS High Sierra

For versions prior to these, you'll need to acquire them outside the App Store. Apple provides direct downloads starting from OS X Yosemite (10.10).

Download these macOS versions via the following links:

• macOS Sierra
• OS X El Capitan
• OS X Yosemite

For even older versions, alternative sources will be necessary. You might find old installation discs being sold on eBay, for example.

Also, note that some of these older downloads arrive as .dmg files. To utilize them, double-click to mount the image, then run the .pkg file inside. This process installs the relevant macOS installer into your Applications folder.

Creating a bootable USB drive for macOS

Once the installer for the older macOS version is downloaded, it needs to be placed onto a bootable medium. A bootable USB drive is the most straightforward option. It could be either an external hard drive or a thumb drive.

While burning the installation files to DVD is possible, this method is slower. Additionally, newer OS X versions exceed standard DVD capacities. Given many Macs lack optical drives entirely, this isn't a practical choice.

The steps to create a bootable USB drive for macOS include:

1. Download the macOS installer.
2. Format your USB drive using Disk Utility.
3. Use Terminal to transfer the installation files to the USB drive.

Alternatively, you can use the free application Disk Creator to make your bootable USB drive. It performs the same function as Terminal commands but through a user-friendly graphical interface.

Steps to create a bootable disk using Disk Creator on Mac:

1. Download and launch Disk Creator.
2. Under Select the volume to become the installer, choose your USB drive.
3. Click Choose a macOS installer.
4. Browse your system to locate the macOS installer within Applications.
5. Press Create Installer and wait while Disk Creator completes the process.

Installing an older macOS version from a USB drive

With a bootable USB drive created, you're ready to begin the macOS installation. This involves selecting the USB drive during startup.

Instructions for using a bootable USB drive on a Mac:

1. Restart or power on your Mac.
2. Before the startup chime, press and hold the Option key.
3. Keep holding until the boot options screen appears.
4. Select your USB drive and allow time for it to load.

If installing to an external drive or new partition, follow the installer prompts. However, Apple does not permit downgrading your current macOS version directly. To install an older version on your main drive, you must first completely erase it.

How to erase your Mac's hard drive before downgrading:

1. After booting from the bootable USB drive, open Disk Utility.
2. From the list on the left, select your primary drive.
3. Click Erase.
4. Assign a name to the drive and set the format to OS X Extended (Journaled)—referred to as Mac OS Extended (Journaled) in later OS versions.
5. Ensure the Scheme is configured to GUID Partition Map.
6. Click Erase and let Disk Utility complete the wiping process.

Returning to the macOS installer, you should now be able to install the older OS X version on your main disk.

FAQ

Should I consider downgrading OS X?

Ideally, avoid doing so. Downgrading means missing out on new features and losing Apple's support. If older third-party software necessitates the downgrade, look for alternatives compatible with the latest macOS versions instead.

If you're downgrading due to sluggish performance after an update, try our Mac speed-up tips first. Also, consider downloading MacKeeper to perform regular scans for junk files and cache clearing, which might eliminate the need for a downgrade altogether.

Can I downgrade my M1 Mac?

M1 Macs utilize a different processor architecture compared to previous Apple computers. As such, they cannot run any macOS version earlier than Big Sur—the initial macOS version supporting M1 chips.

Read More Guides:

• How to Create a High Sierra Bootable USB Drive
• How to Downgrade From Big Sur to Catalina
• How to Install Windows on a Mac

The above is the detailed content of How to Download Old macOS Versions and Install Them. For more information, please follow other related articles on the PHP Chinese website!