Fix a Mac that won't start up

Steps

1. 01

   Rule out power before you rule out macOS

   • No light, no fan, no sound at all? Try a different charger and a different cable, and give it ten minutes on mains before trying again
   • Plug the power adapter in, unplug every other device, and hold Command and Control while pressing the power button to restart
   • A Mac that chimes, lights up or spins a fan is running — that is a startup problem, and the rest of this fix applies

   Why?

   Apple's own sequence for a laptop that has run out of power looks identical to a Mac that refuses to start. Separating the two first saves you an hour in Recovery that was never going to help.

2. 02

   Start up in macOS Recovery

   • Apple silicon: press and hold the power button until 'Loading startup options' appears,then click Options›Continue
   • Intel: press the power button and immediately hold Command (⌘) and R until an Apple logo or a spinning globe appears
   • If asked, pick an administrator account and enter its password

   ✓You should see: The Recovery utilities window, offering Restore From Time Machine, Reinstall macOS, Safari and Disk Utility.

   !Careful: With FileVault on, Recovery asks for a user password before Disk Utility can even see the disk. There is no bypass and no reset — without that password or the recovery key, the data stays encrypted. That is the feature working, not a fault.

   Also see: Can't log in to your Mac: password and FileVault recovery

3. 03

   Repair the disk with First Aid, bottom up

   • Open Disk Utility from the Recovery window,then turn on View›Show All Devices
   • Run First Aid from the bottom layer upwards: the physical device first, then the container, then the volume
   • Let each pass finish before starting the next, and read what it reports rather than clicking through

   ✓You should see: First Aid finishes with no errors at every layer. Restart and see whether the Mac now boots on its own — this alone fixes most startup problems.

   Why?

   Running First Aid on the volume alone is the common mistake: it skips the container and device layers, which are usually where the damage actually is.

   Also see: Run First Aid on external drives

4. 04

   Get your files off before you go further

   • If First Aid reported errors it could not repair, stop here and rescue the data first
   • From Recovery, use Disk Utility to mount the disk and copy your files to an external drive
   • Or hand the whole disk to a second Mac over a cable: on Apple silicon, start up in Recovery and choose Utilities → Share Disk; on an Intel Mac, hold T during startup for Target Disk Mode

   !Careful: Everything after this point either rewrites the system or erases the disk. A disk that First Aid cannot repair is a disk that may fail completely on the next restart — copy what matters off now, while it still mounts.

   Also see: Set up Time Machine properly

5. 05

   Reinstall macOS over the top

   • Back in the Recovery window, choose 'Reinstall macOS' and follow the installer
   • If it offers both 'Macintosh HD' and 'Macintosh HD - Data', choose Macintosh HD
   • Keep it plugged in and don't close the lid until it finishes

   Why?

   Apple states that reinstalling macOS doesn't remove your apps or personal data — it replaces the system, not your files. On an Intel Mac, Recovery may offer the version the machine shipped with rather than the one you were running, and on a slow connection the download takes hours.

   Also see: macOS update won't install: unstick a stalled upgrade