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Before upgrading macOS, back up your files, confirm that your exact Mac model supports the version you want, and check the installer’s storage requirements. Then install through Software Update and keep your Mac awake until the process finishes. Apple does not publish one universal free-space figure for macOS 27, so don’t treat backup-drive sizing guidance as an upgrade requirement.
1. Back up your Mac before upgrading
Apple recommends backing up your files before installing a macOS upgrade. Time Machine is built into macOS, and you can use an external storage device or a supported network destination. See Apple’s Time Machine backup instructions and its list of compatible backup disks.
Choose a backup destination
- External drive: Connect a compatible storage device to a port on your Mac, such as USB-C or Thunderbolt. This is a common Time Machine setup.
- Network storage: Time Machine supports certain network destinations, including another Mac and NAS devices that support Time Machine over SMB. If you rely on older AFP-based network equipment, check Apple’s compatibility notes before upgrading.
Size the backup disk appropriately
Apple’s ideal guideline is to use a backup device with at least twice the storage capacity of your Mac. For example, for a Mac with 1 TB of storage, Apple’s guideline points to a 2 TB backup disk. This is advice about backup-disk capacity—not how much free internal storage macOS needs to install. During setup, Time Machine may ask to erase the selected disk. Confirm that you have selected the right disk and that it contains nothing you need before agreeing.
2. Check whether your Mac supports the new macOS
Compatibility depends on both the macOS release and your exact Mac model. Check Apple’s macOS 27 compatibility information before starting. Apple’s current macOS 27 page describes support for Macs with Apple silicon, including M-series and A-series chips; consult the compatibility list for your specific computer rather than inferring eligibility from the chip family alone.
#1 Best Overall
- Easily store and access 5TB of content on the go with the Seagate portable drive, a USB external hard Drive
- Designed to work with Windows or Mac computers, this external hard drive makes backup a snap just drag and drop
- To get set up, connect the portable hard drive to a computer for automatic recognition software required
- This USB drive provides plug and play simplicity with the included 18 inch USB 3.0 cable
- The available storage capacity may vary.
Software Update filters for compatible software, so it will not offer an update that is incompatible with your Mac. If the version you expect is absent, check Apple’s compatibility information and confirm which macOS release is available for your model.
3. Check available storage without relying on a universal figure
Review your Mac’s available storage before downloading the installer, but don’t assume there is one free-space threshold that applies to every Mac and release. Apple’s reviewed upgrade instructions do not state a universal amount of free internal storage required for macOS 27. Follow the current installer’s prompts and Apple’s guidance for your model. Apple also notes that Software Update may use less storage to download and install macOS than other installation methods.
Rank #2
- Easily store and access 1TB to content on the go with the Seagate Portable Drive, a USB external hard drive.Specific uses: Personal
- Designed to work with Windows or Mac computers, this external hard drive makes backup a snap just drag and drop. Reformatting may be required for Mac
- To get set up, connect the portable hard drive to a computer for automatic recognition no software required
- This USB drive provides plug and play simplicity with the included 18 inch USB 3.0 cable
- The available storage capacity may vary.
The Time Machine guideline of twice your Mac’s storage describes the capacity of a backup destination. It does not tell you how much room to clear on your Mac to upgrade.
4. Check essential apps and save your work
Save open work and close apps before beginning. If a third-party app, driver, or work tool must function immediately after the upgrade, check its developer’s current support information for the macOS version you plan to install. Apple’s general upgrade instructions do not establish compatibility for individual third-party apps.
Rank #3
- Easily store and access 4TB of content on the go with the Seagate Portable Drive, a USB external hard drive.Specific uses: Personal
- Designed to work with Windows or Mac computers, this external hard drive makes backup a snap just drag and drop
- To get set up, connect the portable hard drive to a computer for automatic recognition no software required
- This USB drive provides plug and play simplicity with the included 18 inch USB 3.0 cable
- The available storage capacity may vary.
5. Install through Software Update
Apple recommends Software Update as the easiest way to find and install compatible macOS updates. It checks for available Apple software and offers only updates compatible with your Mac. Open it using either route:
- Press Command-Space to open Spotlight, search for Software Update, and open it.
- Choose Apple menu > System Settings > General > Software Update.
- Wait while Software Update checks for available software.
- Review the update or upgrade it offers, then choose the available control, such as Update, Upgrade, or Restart Now.
- Enter your administrator password if prompted, then follow the on-screen instructions.
Apple says Software Update can use less storage than other installation methods. For cases where it fails or the Mac cannot start normally, Apple describes macOS Recovery and other installation methods. A bootable installer can be useful for specialized situations, such as installing on multiple computers without downloading the installer each time, but it is not the usual preparation route for one Mac.
Rank #4
- High capacity in a small enclosure – The small, lightweight design offers up to 6TB* capacity, making WD Elements portable hard drives the ideal companion for consumers on the go.
- Plug-and-play expandability
- Vast capacities up to 6TB[1] to store your photos, videos, music, important documents and more
- SuperSpeed USB 3.2 Gen 1 (5Gbps)
6. Keep the Mac awake until installation finishes
Do not put the Mac to sleep during installation or close a laptop’s lid. Restarts, progress bars, and blank screens may appear several times while the upgrade completes. Leave the Mac undisturbed until the installation is finished; Apple’s macOS update instructions describe what to expect.
Quick Recap
Best Value
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- Compatibility: compatible with PS4/xbox one/Windows/Linux/Mac/Android,Stable and fast downloading on game console no difference from fast transmission when using on PC.
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- Package Contents: 1* portable hard drive, 1 *USB 3.0 cable, 1*USB to type C adapter，1 *user manual, shell packaging, three-year manufacturer's warranty and free technical support services
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