To reinstall macOS, you must first use Recovery mode to access the system recovery menu. However, if you want to make sure that everything remains intact, you should use Time machine. Everything including customizations, photos, and apps will remain. While formatting your Mac does delete files and settings, reinstalling it does not.

Reinstalling MacOS can help you solve a variety of problems. How Do I Reinstall My Mac Startup Disk?.Does Reinstalling Mac Delete Everything?.Why is My Mac Not Letting Me Reinstall macOS?.If you do not find any troubleshooting information in the Recovery Mode, use the Disk Utility to reinstall macOS High Sierra. Then, select Recovery Mode over the Internet. Alternatively, you can perform a clean installation by pressing Option-Command-R while your Mac is connected to the Internet. If this doesn’t work, you can also reinstall macOS High Sierra using a Time Machine backup. Once you have a time machine backup of your data, use it to restore Sierra. In case you are asked for administrator credentials, click on the “Add helper” option.

You will be guided through the process step by step. Once you have the installer file, launch it by pressing Command-R and selecting the “Restore from Time Machine” option. First, download the “Install macOS High Sierra” installer file from the Applications folder. Manual reinstallation requires less knowledge and skill, while automatic reinstallation requires time and patience. If you have a problem with macOS High Sierra and would like to reinstall the OS, you can choose to do it manually or automatically.

Reinstall macos high sierra