How to reinstall macOS without losing your files

What a reinstall does, and what it leaves alone

Reinstalling replaces the operating system while keeping the existing installation's apps and personal data. It is different from erasing, downgrading or starting with a blank account. Apple's reinstallation instructions explicitly say that reinstalling doesn't remove apps or personal data and still recommend a backup.

That makes it a reasonable later step when macOS won't work correctly or a normal installation repeatedly fails. It is not a general clean-up method. If the cause is one incompatible app, a full disk, a failing drive or the files in your own account, keeping those things can also keep the problem.

If the desktop works and your aim is simply to install a newer release, start with Software Update. If you are selling or giving away the Mac, use the factory-reset procedure; reinstalling over your account leaves personal information behind.

Before reinstalling: protect the current data

1. Make a backup if the Mac can start. Complete a Time Machine backup or copy essential documents to a separate storage device. Check that the files you care about are actually in that copy.
2. Keep the login password available. Recovery may ask you to select a user and unlock the disk. This is the Mac account's password, not a prompt to give a password to an online repair service.
3. Connect a MacBook to power. Leave the lid open for installation. For a desktop, keep power and the display connection stable.
4. Use suitable internet. Apple's Recovery installer needs broadband using DHCP over Wi-Fi or Ethernet. Networks requiring a captive browser login, 802.1X authentication or direct PPPoE can prevent installation.
5. Record the problem. Note the exact error and whether it happens before login or inside an app. That gives you a useful comparison after reinstalling.

If the Mac won't start and the files are not backed up, pause before doing anything that says Erase or Restore. Our Recovery guide explains Share Disk, which can make accessible files available to another Mac. It doesn't bypass disk encryption, and a disk that is physically failing may need specialist advice before more work.

How to reinstall macOS from Recovery

On Apple silicon, enter Recovery by shutting down, holding the power button until startup options appear, then selecting Options › Continue. The entry method and Recovery utility names are documented for macOS 15 Sequoia, macOS 26 Tahoe and macOS 27 Golden Gate. The linked Recovery guide owns the detailed startup instructions.

1. Open Reinstall macOS [name]. Select the install or reinstall option in Recovery's main window and click Continue. The name tells you which operating system the installer is offering.
2. Follow the installer. Read the licence and destination choices. If asked to unlock the disk, use the password you normally use to log in to this Mac.
3. Select the existing system volume. If offered both Macintosh HD and Macintosh HD - Data, Apple says to choose Macintosh HD. If you renamed it, identify the intended system volume rather than choosing a similarly named external disk.
4. Keep the disk intact. Do not open Disk Utility and erase it as a preparation step for this procedure. If the installer won't accept or see the disk, stop and read the troubleshooting section below.
5. Let installation finish. Don't close the lid or put the Mac to sleep. Restarts, a progress bar that appears again and a blank screen lasting minutes can occur.
6. Complete any setup prompts. Once back at the desktop, open your important files and check the original fault before making further changes.

On an Intel Mac, the Recovery startup shortcuts differ. Use Apple's instructions for Intel. Don't assume that a familiar Intel Internet Recovery combination selects the same version or mode on Apple silicon.

Which macOS will install, and how long it takes

Apple says Recovery on Apple silicon installs the current version of the macOS most recently installed. It is not an open version picker. Apple also documents an exception after an upgrade followed by a Disk Utility erase: Recovery may offer the version used before the upgrade.

Read the installer's displayed name. If it isn't the version you expected, don't erase the disk to try to force a choice. After a successful reinstall you can check for a supported update in System Settings › General › Software Update.

Apple doesn't give a universal time estimate for the whole reinstall. The download, disk work and setup vary. Its instructions specifically warn that the screen may be blank for minutes and that restarts can occur several times. For an update or upgrade, Apple's startup article recommends allowing overnight if needed.

Plan a period when you don't need the Mac, keep it powered and avoid using a stalled time-remaining estimate as your only evidence of failure. An explicit error, a repeating boot loop and an installer still progressing are different situations.

If the installer fails or cannot see the disk

Start with the actual message. Apple's installation-error checklist covers space, internet access, Recovery, disk repair and, rarely, firmware repair. Record where the error occurred so a second attempt tests something specific.

• Not enough space: if you can reach macOS, use System Settings › General › Storage to review large files you recognize. Back them up before removal. Reinstalling doesn't create free space by removing your personal files.
• Download or connection failure: try a suitable stable network. Recovery's connection requirements can exclude a network that works for ordinary browsing after login.
• Disk errors: Apple's repair procedure uses Disk Utility First Aid from Recovery. First Aid is different from Erase; read the selection carefully.
• Disk absent or still unusable: Apple's reinstall article presents erasing as a later step and says a disk that cannot be seen or erased may need service. If keeping unbacked-up files is your priority, stop and get advice before accepting an erase.
• Recovery itself unavailable: firmware revival or service may be necessary. Get the model-specific Apple instructions rather than repeatedly attempting an unrelated reinstall method.

If the installation error persists, contact Apple Support. Keep your backup situation explicit: “I have a current backup” and “these files are the only copy” lead to different sensible next steps.

Check the original problem after reinstalling

Confirm the macOS version in Apple menu › About This Mac. Open the document or task that previously failed. Check required apps and accessories before treating the operation as complete, then make a fresh backup once you have verified the data.

If the same app still misbehaves, update or troubleshoot that app with its developer. If the whole Mac still hangs or restarts, Apple Diagnostics can add hardware evidence. A reinstall that leaves a fault unchanged is useful information; it doesn't justify a cycle of erase-and-reinstall attempts.

Where Tend fits

Tend can't run in Recovery or help while the Mac won't start. Once it starts, its free CPU, memory and estimated per-app power readings can help check the workload that caused concern. Energy history is stored in your own Library on the Mac, so a non-erasing reinstall is intended to retain it along with your account; an erase removes that local history unless it is restored from a backup.

Questions

Related guides

Sources

Sources checked 23 October 2026. These are documented steps and specifications; no repair, installation or performance test was run for this guide.

• Apple, How to reinstall macOS
• Apple, How to start up from macOS Recovery
• Apple, Use Recovery on Apple silicon — macOS 15
• Apple, Use Recovery on Apple silicon — macOS 26
• Apple, If an error occurred while updating or installing macOS
• Apple, If your Mac starts up to an Apple logo or progress bar

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