Summary: This post introduces the meaning of the prohibitory symbol on Mac. You'll know how to get rid of this sign of a circle with a line (or slash crossed out circle), and then boot up your MacBook Pro, MacBook Air, iMac, and Mac mini as usual.
The sign, a circle with a line through it, is one of the most common symbols you could see on Mac startup. But it's definitely not the bearer of good news, but indicates problems when Mac is booting up.
What does a circle with a line through it mean at Mac startup?
Different from the Mac folder with a question mark issue, a circle with a line or slash through it means that your selected startup disk has a Mac operating system that can't be used by your Mac model.
To make it straightforward, Mac does detect an operating system in the startup disk, but it can't boot from that version or build. And then feedback it with the circle with a slash sign on Mac boot.
Some try to downgrade macOS Big Sur to older system with Time Machine backup, only to find that prohibitory symbol at Mac startup due to incompatible OS.
Then how to get rid of this circle with slash symbol and turn on your Mac?
Guide to Fix the Prohibitory Symbol on Mac
To help Mac boot past the prohibitory symbol, you can follow these steps.
Step 1. Boot the Mac into macOS Recovery mode
If you can't boot up Mac in a normal way because it's stuck on the prohibitory symbol screen, then you can try to boot Mac into macOS Recovery Mode, either from the local recovery system on your startup disk or internet recovery system.
Here is how to do this.
- 1. Force your Mac to shut down by holding the power button for 5 seconds around.
- 2. Restart the Mac and instantly hold Command + R key combinations.
- 3. Release these keys when you see the Apple logo or loading bar. Then you'll see the macOS Utilities, which means your Mac is in macOS Recovery mode.
Note: If you can't boot into macOS Recovery mode by the guide above, you can replace the key combinations with Option + Command + R (or Shift+ Option + Command + R), and keep your Mac connecting to the Internet.
If you are using an Apple M1 Mac and see this circle with a line through it, the way to boot into & Use M1 Mac Recovery Mode is different.
Step 2: Repair the startup disk with Disk Utility
You may also see this prohibitory sign on your Mac if the Macintosh HD is corrupted.
Disk Utility can find and repair errors that lead to Mac's unexpected behaviours that prevent your Mac from turning on. So, when your Mac won't boot past the sign of a circle with a line through it, simply check, verify, and repair the startup disk in macOS Recovery mode.
If Disk Utility succeeds in repairing the errors in the startup disk, you can quit Disk Utility and reboot your Mac as normal. If Disk Utility found no errors, continue with the next movement.
If unfortunately, you can't access Disk Utility because macOS Recovery mode is not working, you may want to try Target Disk Mode.
It turns your troubled Mac into an external drive. Do this by connecting your troubled device to another Mac with the same OS or higher and restarting it while pressing the “T” key. Then you can open Dick Utility on the other Mac, select the troubled hard drive and click repair.
Step 3: Back up files from the Mac and reinstall macOS
If First Aid fails to repair the startup disk, then it should be the incompatible Mac operating system that causes the prohibitory symbol on Mac boot. It happens when:
- you upgrade to the latest macOS but it not compatible with your machine
- the macOS build or version on your startup disk is damaged
- you downgrade the system from Time Machine backup and cause software conflict
Then, you can only reinstall a macOS that work with your Mac models.
However, you should know that macOS reinstallation could risk losing your data on the Mac. Your files could get lost or deleted sometimes, so make sure you have a backup of your data. If you don't, you can also get data off the Mac that won't turn on first.
After your files are retrieved from the Mac that boots to a prohibitory symbol, or if you don't worry about data loss, you can move to reinstall the macOS.
After all these steps, you can restart your Mac to see whether the annoying sign of a circle with a line through it has disappeared or not. Hopefully, you'll get rid of this prohibitory symbol when Mac is booting up.
But if the startup disk is not detected in Disk Utility or by the macOS reinstallation wizard, it means your hard drive has failed and needs to be replaced. Or, you may want to contact Apple support for help.