Optional: If you previously used Disk Utility to add internal volumes other than Macintosh HD, you can erase them individually using the same process.

If this button isn't shown, click Erase instead.

Format: APFS or Mac OS Extended (Journaled), as recommended by Disk Utility.

Click the Erase button in the toolbar, then enter the requested details:.

Select Macintosh HD in the sidebar of Disk Utility.

From the utilities window, select Disk Utility and click Continue.

If asked, select a user you know the password for, then enter their administrator password.

Start up from macOS Recovery: Turn on your Mac, then immediately press and hold these two keys until you see an Apple logo or other image: Command (⌘) and R.

If you are having a specific issue, please search Ask Different for a solution and if you didn't find any, ask a new question. You can also use cloud services to keep some of your files safe. You can then restore all your data in case you upgrade to a new Mac or something unexpected happens.

Your Mac will create hourly backups for as long as the Time Machine drive is reachable. On a Mac, you can setup Time Machine and keep it running. It's always advisable to have backups of your data. When upgrading to another Mac I just restore my Time Machine data or use the Migration Assistant (both are built-in on macOS). Personally, I've been updating macOS on my devices for several years without formatting, I guess ever since macOS Mavericks. If you format the whole drive, you will lose both volumes and have to reinstall macOS, after which it will ask if you want to restore your data from a Time Machine backup.If you format the data volume, you will lose all of your data, but the OS will remain functional.

If you reinstall macOS, it only makes changes to the OS volume, and you will not even realize macOS was reinstalled because it will reboot and everything will remain exactly where it was, even any windows you had open before reinstalling macOS.Macs have separate volumes for the OS and for user data. If you know the cause or are willing to troubleshoot the issue, you could fix most problems without formatting your Mac. Even if you are having problems, it doesn't mean you need to format it. Unless you are experiencing serious issues (such as malware or other unexpected behavior), there's no need to ever reset/format a Mac.

Reformat macbook pro