Mac Prohibitory Symbol on Startup

Mac prohibitory symbol (circle with a line through it) on startup means the Mac found a startup disk but macOS is not compatible or is corrupted. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: Circle with a line displayed during boot. macOS found on the disk is incompatible with this Mac. System files may be corrupted beyond repair. Different from the flashing folder (which means no disk found). Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: macOS version incompatible with Mac hardware. System files critically corrupted. Target Disk Mode detected incompatible OS. Boot sector or core system files damaged. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Boot into Recovery Mode (Command+R) and reinstall macOS. Reset NVRAM and try booting again. Use Internet Recovery (Option+Command+R) if local Recovery fails. Erase and clean install macOS from Recovery. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Mac Error Codes collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.