Reformatting your Mac, also known as wiping or erasing your Mac, is the process of deleting all the data on the startup drive and reinstalling the operating system. This is usually done to start fresh with a clean installation of macOS, resolve persistent software issues, or remove malware. Reformatting completely erases the contents of the startup drive and restores the Mac to its original factory settings.
Why would I need to reformat my Mac?
There are several reasons why you may want or need to reformat your Mac:
- You’re selling or giving away your Mac – Reformatting the drive erases all your personal data and starts fresh for the new owner.
- Persistent software issues or crashes – A clean install can resolve problems caused by outdated, corrupt or incompatible apps, files or settings.
- Switching macOS versions – Upgrading to a new major version of macOS often requires a clean install to avoid migration issues.
- Malware infection – Reformatting completely removes stubborn malware that standard antivirus software cannot eliminate.
- General performance issues – Over time, cruft can build up and slow down your Mac. Reformatting restores optimal performance.
In summary, reformatting your Mac wipes the drive clean, eliminates problematic files/settings, restores factory settings, removes malware, and optimizes system performance.
What exactly happens when I reformat my Mac?
Here is an overview of the key steps involved when you reformat a Mac:
- Backup essential data – Before erasing, ensure important files are backed up to iCloud, Time Machine or an external drive.
- Erase the startup drive – Using Disk Utility, erase and reformat the internal drive that contains the OS. This deletes all data.
- Clean install macOS – With the empty, wiped drive, proceed with a clean install of the desired macOS version.
- Configure Mac – Go through first-time setup, create a new user account and configure preferences/settings.
- Reinstall apps – Download apps fresh from the App Store or web, don’t use old app backups.
- Restore data – Import documents, media, settings from backups. Don’t restore system files or apps.
The result is a Mac with a fresh OS, new user accounts, current apps and personal data/settings. All old system files, problematic data, malware and unwanted apps are wiped clean.
How do I reformat my Mac step-by-step?
Here is a step-by-step walkthrough on how to reformat your Mac:
- Backup data – Use Time Machine, iCloud or an external drive to backup all important files.
- Sign out of Apple services – Sign out of iCloud, iMessage, FaceTime, iTunes, App Store etc.
- Boot into Recovery mode – Hold Command + R while restarting, then select Disk Utility.
- Select startup disk – Click on the disk containing the OS you want to reformat (usually Macintosh HD).
- Erase disk – Click Erase, name it if desired, Format: Mac OS Extended (Journaled).
- Exit Disk Utility – After successful erase, click Done and exit Disk Utility.
- Reinstall macOS – Follow prompts to reinstall macOS clean on wiped drive.
- Complete Setup Assistant – Create a new admin user account and complete configuring Mac.
- Install apps – Download and reinstall apps fresh from the App Store.
- Import data – Transfer documents, media, settings from backups.
Be sure to only restore personal data and settings, not old system files or apps. You now have a fresh Mac!
What will I lose when reformatting my Mac?
Reformatting your Mac’s startup drive will delete:
- All files and folders in your user account
- Apps and app data
- System settings and preferences
- macOS system files
- Cached and temporary files
- Malware, unwanted apps, Registry issues (in Windows)
Essentially, the entire contents of your startup drive will be deleted. That’s why it’s crucial to have a complete backup before reformatting.
What data will be saved when reformatting Mac?
Reformatting will NOT delete data stored separately from the startup drive, such as:
- iCloud content – Contacts, Calendar, Find My Mac, Photos, etc.
- Files on external drives
- Time Machine or other backup drive data
- Music, movies, books synced to iTunes
- Handoff content synced to other Apple devices
As long as you backup your startup drive before erasing, your personal content will be preserved on external devices or cloud services.
How long does reformatting a Mac take?
The time to reformat a Mac can range from 30 minutes to a few hours, depending on:
- Erase method – A simple erase is faster than a secure multi-pass erase.
- Drive size – Larger capacity hard drives take longer to reformat.
- Drive type – SSDs reformat significantly faster than traditional hard disk drives.
- Mac model – Newer Macs with faster processors erase quicker.
- macOS version – New installs usually go faster than older OS versions.
- Data load – Restoring large amounts of data adds more time.
For reference, erasing and reinstalling macOS on a base model 256GB MacBook Air with an SSD would take around 30-60 minutes. Restoring data could add 1-2 hours.
How can I speed up reformatting my Mac?
Tips to reduce reformatting time:
- Use a fast SSD startup drive
- Erase using simple 1-pass method
- Have latest macOS installer ready
- Use wired internet connection
- Disconnect peripherals
- Use Activity Monitor to quit other processes
- Only migrate essential data, not full backups
- Limit number of apps installed initially
- Enable trim on third-party SSDs
Following these tips will help streamline the reformat and reinstallation process, avoiding long waits. Avoid interrupting the process once started.
Can I reformat a Mac without losing data?
It is not possible to reformat the startup drive on a Mac without losing data. The reformatting process inherently erases the entire drive contents. However, there are options to preserve your files:
- Backup to external drive – Manually backup all needed data to an external USB drive.
- Use Time Machine – Have a Time Machine backup ready to restore files after.
- Store on cloud – Sync important documents and photos to iCloud.
- Create disk partition – Partition drive to store data separately from OS.
As long as you have backups on other drives or storage services, you can safely reformat the startup drive while retaining your personal files and settings.
Can I reinstall macOS without erasing drive?
There are a couple of options to reinstall macOS non-destructively:
- Archive and Install – Reinstalls macOS but preserves user data.
- Upgrade install – Installs major macOS version updates in-place.
- Restore from Time Machine – Reverts machine state to Time Machine backup.
However, these methods may retain old problems and files. For a completely clean slate, erasing the drive before reinstalling macOS is recommended.
Should I reformat my Mac before selling it?
Yes, you should absolutely reformat your Mac before selling it or giving it away. This is to erase all your personal data for security and privacy reasons. Specific steps:
- Backup all your personal files and data.
- Sign out of all accounts like iCloud, iTunes, iMessage, etc.
- Use Disk Utility to securely erase the startup drive.
- Reinstall a fresh copy of macOS.
- Unlink the Mac from your Apple ID in your account settings.
This will wipe the Mac completely while removing any association with your accounts. The new owner will get a fresh Mac to setup themselves.
What will I need to reconfigure after reformatting my Mac?
Here are some key things you’ll need to reconfigure after reformatting your Mac:
- User accounts and passwords
- Re-purchase and reinstall apps
- macOS preferences and settings
- Desktop layout and finder settings
- Photos, iMovie and Garageband media libraries
- Sign back into iCloud, iTunes and App Store
- Set up printers, scanners and other devices
- Configure Time Machine backups
- Customized toolbar items and menu bar settings
Expect to spend a few hours repersonalizing your Mac after reformatting. Use it as an opportunity to declutter and streamline your setup.
What will stay the same after reformatting Mac?
A few things that will remain unchanged after erasing and reinstalling macOS:
- Wallpaper and certain System Preferences (if restored)
- Find My Mac activation
- Handoff connections to Apple devices
- SMS relay to iPhone (with iMessage reactivation)
- Wi-Fi networks and passwords
- Keychains (if unencrypted)
- SIP and firmware passwords
However, most system settings, apps and accounts will need to be reconfigured from scratch after reformatting for a fresh experience.
Should I reformat SSD and HDD differently?
Here are some key reformat differences between SSDs and HDDs:
| SSD | HDD |
|---|---|
| APFS format optimal | Mac OS Extended better |
| Faster 1-pass erase | Multi-pass erase recommended |
| Trim enabled improves performance | Defrag occasionally to optimize |
| Higher reformat resilience | More prone to bad sectors |
Tailor the reformat method based on drive type for best results. SSDs streamline the process.
How can I securely erase data when reformatting?
To prevent any chance of data recovery when reformatting, use these secure erase options:
- Multi-pass erase – Overwrite drive with multiple passes of random data.
- FileVault encryption – Encrypt the disk before erasing for added protection.
- Secure tokens – Generate secure tokens for Apple ID, iCloud and Find My.
- Deauthorize services – Sign out of iTunes, iMessage, etc to disassociate.
- Remove activation lock – Release device from activation lock before erasing.
Take these precautions when selling or disposing of your Mac to prevent data recovery.
Can I restore apps and settings after reformatting Mac?
It’s not recommended to restore apps and settings from a backup after reformatting your Mac. This risks bringing back problematic files, malware or incompatibilities. Better to start fresh where possible.
However, you can selectively restore some data:
- Documents and media files
- Keychain passwords
- Browser bookmarks
Use your judgement on what to restore versus setting up as new. A hybrid approach keeps your data while optimizing system performance.
Conclusion
Reformatting your Mac provides a clean slate that resolves many system issues, removes malware, and restores performance. The process completely erases all data from the startup drive, requiring backups be made ahead of time. Following best practices tailored for HDDs versus SSDs, using secure erase options, and selectively restoring data will result in an optimized Mac.