Boot into verbose mode to see where it stops, and remember you can always boot from the OCLP USB installer's OpenCore and rebuild from there — a Mac that won't boot is almost never a Mac that can't be recovered.
Prohibited sign means OpenCore isn't loading. Stall near the end of the progress bar usually means root patches are wrong for the installed macOS. Reboot loop usually means a mismatch between your OpenCore config and the OS.
Read the screen first
| What's on screen | Which stage failed | Most likely cause |
|---|---|---|
| Circle with a line through it (prohibited sign) | Before macOS starts — OpenCore isn't handing off | OpenCore missing or damaged on the EFI partition, or the Mac is booting the wrong disk |
| Apple logo, no progress bar, indefinitely | Very early boot | Wrong SMBIOS spoof, or an OpenCore config from a different Mac |
| Progress bar reaches roughly 90–100% then stalls or restarts | Late kernel / driver load | Root patches mismatched with the installed macOS — very common straight after an update |
| Reboots repeatedly, never reaching the login window | Kernel panic during startup | OCLP build too old for this macOS, or an incomplete patch run |
| Login window appears but the desktop never draws properly | macOS is up; graphics are not | Acceleration, not boot — see sluggish graphics |
Turn on verbose mode — stop guessing
Verbose boot replaces the Apple logo with the actual kernel log, and the last few lines before it freezes tell you what failed. It is the difference between diagnosing this in two minutes and thrashing for an hour.
Hold Command + V immediately after the startup chime or the moment the screen lights up. On a Mac booting through OpenCore you can also press Space at the boot picker to reveal extra options, then choose the verbose entry.
Photograph the last visible lines with your phone. Even if they mean nothing to you, they're exactly what anyone helping you will ask for, and they usually name the offending kext outright.
The recovery path that works from almost anywhere
Your OCLP USB installer is not just for installing. It carries its own copy of OpenCore, so it can boot a Mac whose internal OpenCore is broken:
Boot from the USB.
Hold Option at startup, choose the EFI Boot entry on the USB — not the macOS installer entry directly.
From that boot picker, select your internal drive.
You're now running your normal macOS install, but through the USB's OpenCore. If this works, your installed system is fine and only the internal EFI is broken — good news.
Open OCLP and rebuild.
Build and Install OpenCore, target the internal disk. This replaces the broken EFI contents with a fresh, correct build.
Reapply root patches if the desktop looks wrong.
Then reboot without the USB and confirm the Mac comes up on its own.
Make the installer USB before you need it, and keep it. A 16 GB stick sitting in a drawer converts most OCLP disasters into twenty-minute inconveniences. It is the single most useful thing you can own for a patched Mac.
Fixes for specific stages
Prohibited sign. OpenCore isn't loading at all. Reset NVRAM (Option + Command + P + R at power-on) so the Mac forgets a stale boot selection, then hold Option and pick the OpenCore entry manually. If no such entry exists, OpenCore is gone from the EFI partition — rebuild it via the USB route above.
Stall at the end of the progress bar. Nearly always root patches that don't match the installed macOS, which is why it appears right after an update. Boot via the USB, run OCLP, and either reapply patches for the current OS or revert them and reapply cleanly.
Reboot loop. Usually an OCLP build predating your macOS. Boot through the USB, install current OCLP, rebuild OpenCore, reapply patches.
Nothing at all — black screen, no chime, no light. That's not OCLP. Software cannot prevent a Mac from powering on. Look at power, battery, and display hardware.
When it's the hardware, not the patch
Some 2011 MacBook Pros and iMacs have a well-documented discrete GPU failure that produces boot hangs, garbled output and coloured artefacts. Two signs distinguish it from anything OCLP did:
- Artefacts appear before macOS starts loading — at the Apple logo, or in the boot picker itself. No software running on the Mac at that point could cause it.
- Booting into Safe Mode or an entirely different OS shows the same corruption.
If that matches, no amount of repatching helps. The usual workaround is disabling the discrete GPU so the Mac runs on integrated graphics only — well documented for those specific models, and a different procedure from anything on this page.
Common questions
Can I get my files off a Mac that won't boot?
Yes. Target Disk Mode (hold T at startup) presents the internal drive to another Mac over Thunderbolt or FireWire, and it doesn't depend on OpenCore or macOS booting at all. Do this before attempting anything drastic.
Will reinstalling macOS fix it?
Usually unnecessary and often it doesn't help, because the failure is typically in OpenCore or the patch state rather than the OS itself. Rebuild OpenCore from the USB first — it's twenty minutes against several hours.
The Mac boots fine with the USB inserted but not without it.
Then OpenCore is present on the USB and missing or broken on the internal disk. Boot via USB, run OCLP → Build and Install OpenCore, and target the internal drive.