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Mac User Guide
- Welcome
- What’s new in macOS Sequoia
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- Intro to Continuity
- Use AirDrop to send items to nearby devices
- Hand off tasks between devices
- Control your iPhone from your Mac
- Copy and paste between devices
- Stream video and audio with AirPlay
- Make and receive calls and text messages on your Mac
- Use your iPhone internet connection with your Mac
- Share your Wi-Fi password with another device
- Use iPhone as a webcam
- Insert sketches, photos, and scans from iPhone or iPad
- Unlock your Mac with Apple Watch
- Use your iPad as a second display
- Use one keyboard and mouse to control Mac and iPad
- Sync music, books, and more between devices
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- Control what you share
- Set up your Mac to be secure
- Allow apps to see the location of your Mac
- Use Private Browsing
- Keep your data safe
- Understand passwords
- Change weak or compromised passwords
- Keep your Apple Account secure
- Use Mail Privacy Protection
- Use Sign in with Apple for apps and websites
- Find a missing device
- Resources for your Mac
- Resources for your Apple devices
- Copyright
Determine which disk started up your Mac
Some Mac computers can be started up from a network volume, a different disk, or another operating system.
Important: If you have a Mac with an Apple T2 Security Chip, added security features may be set to prevent the computer from starting up from an external startup disk. See What is the Startup Security Utility? If you have a Mac with Apple silicon, see Change the security policy.
On your Mac, choose Apple menu > System Settings, then click General in the sidebar. (You may need to scroll down.)
Click Startup Disk on the right.
Open Startup Disk settings for me
Your startup disk appears selected.
See alsoChange your Mac startup disk
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