Should I format Mac?

Formatting a Mac means erasing all data and settings on the Mac’s hard drive and reinstalling the operating system from scratch. This process completely wipes the hard drive and returns the Mac to its original factory settings. Formatting is recommended before selling or gifting a Mac, to resolve persistent software issues, or to start fresh with a new operating system install. It should not be taken lightly, as formatting will permanently erase all user data, applications, and customizations on the Mac. However, with proper backups, formatting can provide a clean slate and often improves system performance on older Macs. This guide will cover the pros and cons, steps, and best practices for formatting a Mac.

Pros of Formatting

Formatting your Mac can help wipe clean a slow or buggy system and improve performance (source). When a Mac starts running slowly or exhibiting system crashes, it’s often because the disk has become cluttered with old files, caches, logs etc. Doing a clean install by formatting the disk essentially gives you a fresh start. It clears out all the junk and starts you off with a clean, optimized file system. This can “rejuvenate” an older Mac and make it run faster again.

Formatting also helps resolve file system corruption issues. The Mac file system can become corrupt over time, leading to instability and crashes. Formatting completely resets everything and rebuilds a healthy file system from scratch.

Additionally, formatting optimizes the file system for performance. For example, Mac OS Extended (HFS+) can become fragmented over time, slowing down file access. Formatting defragments the disk by erasing everything and laying it out fresh again.

Cons of Formatting

The main disadvantage of formatting your Mac is that you will lose all of your data. When you format, or “wipe”, the hard drive, everything is erased and the computer is returned to its factory settings. This means you will lose all your documents, photos, music, applications, settings, and any other personal files (1). Make sure to back up any important data before formatting.

According to a discussion on the Apple forums, formatting will delete everything on the hard drive and it cannot be reversed, so think carefully before doing it (2). The only way to recover lost files after formatting is if you have a backup.



Back Up Data First

It is crucial to back up your Mac’s data before formatting the hard drive. Formatting will erase all data, files, photos, music, applications, and settings on the drive. According to Apple Support, Time Machine is the built-in backup utility on Mac that can regularly back up everything on your Mac. Users should connect an external hard drive to use for Time Machine backups. Open System Preferences > Time Machine to set up automatic backups before formatting.

Backups allow you to recover your personal data should anything happen during or after formatting the hard drive. Without a current backup, formatting would result in permanent data loss. Apple recommends all users back up their Mac to an external drive or cloud service on a regular basis to avoid catastrophe.

Alternative Fixes

Before deciding to format your Mac, there are some alternative fixes you may want to try first that could resolve your issues without deleting everything. Some options include:

Using a disk repair utility like Paragon HDM to check for and repair disk errors, bad sectors, and file system problems. Third-party disk utilities sometimes can fix issues the built-in Disk Utility cannot.

Clearing up storage space by deleting unused files and applications. Lack of free space can cause performance issues, so freeing up disk space may help.

Reinstalling the Mac operating system without deleting your data, which could resolve software issues or glitches from a failed installation or update.

Trying fixes like Onyx to clear caches, run maintenance scripts, and tune up your Mac.

These alternative options could potentially get your Mac running normally again without resorting to completely wiping the drive and formatting.

When to Format

Formatting your Mac’s hard drive can help improve performance and fix issues in some situations. Some signs it may be time to format include:

Your Mac is running very slow – Formatting will wipe the drive and do a clean install of the operating system, which can eliminate software issues slowing things down.

You are getting random crashes and errors – An underlying file system issue that formatting resolves could be causing system instability.

You want to erase all data before selling or giving away your Mac – Formatting erases all data from the drive.

You need to resolve a partition issue – Formatting will delete all partitions and allow you to repartition the drive.

You upgrade to a new Mac operating system – Doing a clean install via formatting can prevent OS upgrade issues.

There are signs of malware, viruses, or other system infection – Formatting completely resets the system software.

You experience frequent application crashes – An application or associated files may be corrupted, so formatting provides a clean slate.

You forgot your FileVault encryption password – Formatting lets you start over from scratch.

There are often good reasons to do a clean install and formatting when troubleshooting or preparing to sell a Mac. But it should not be necessary for regular maintenance.

How to Format

Here is a step-by-step guide to formatting your Mac:

  1. Back up your Mac using Time Machine or another backup method before formatting to avoid permanent data loss. Be sure to copy any important files to an external hard drive or cloud storage.
  2. Restart your Mac and immediately press and hold Command-R to boot into Recovery mode.
  3. In the Recovery window, select Disk Utility then click Continue.
  4. In Disk Utility, select your startup disk from the sidebar. Click Erase at the top.
  5. Choose a format for the disk – APFS is recommended for newer Macs. Name your disk.
  6. Click Erase to begin formatting the drive. This may take awhile depending on your disk size.
  7. Once complete, quit Disk Utility, then choose Reinstall macOS from the Recovery window to begin reinstalling the operating system.
  8. Follow the onscreen prompts to reinstall MacOS and set up your Mac.

For a more detailed step-by-step guide, refer to Apple’s support article on erasing and reinstalling macOS.

Recovering Data After Formatting

If you accidentally formatted your Mac’s hard drive and need to recover lost files, there are a few options for data recovery:

Use data recovery software like Disk Drill or EaseUS Data Recovery to scan your formatted drive and restore deleted files. These tools can recover documents, photos, videos, music, and more.

Take your Mac to a data recovery service. Professionals have specialized tools to extract data from formatted drives. This is more expensive but may recover more data.

Recover your data from a Time Machine backup if you had one configured before formatting the drive. Time Machine makes it easy to restore lost files.

If you stored files in cloud services like iCloud, Dropbox or Google Drive, you may be able to restore the online copies of those files.

What to Do After Formatting

After formatting your Mac, there are a few steps you’ll need to take to get it set back up.

First, you’ll need to reinstall macOS using the latest installer from the App Store. Follow the prompts to install the operating system (Erase and reinstall macOS – Apple Support).

Once macOS is installed, you can start reinstalling your apps from the App Store or other sources. It’s a good idea to make a list of all the apps you use regularly so you can get them set back up.

You’ll also want to adjust some system preferences to get them back to how you had them before. Go through System Preferences and reset any customizations you had for desktop images, Dock settings, user accounts, and more.

If you used iCloud for backups, you can sign back in to iCloud to restore your contacts, calendars, documents and more. Check that key data has been restored properly.

Finally, be sure to update your Mac with the latest software updates. Go to System Preferences > Software Update to check for and install any macOS updates, security patches, etc.


In summary, formatting your Mac can help improve performance and fix certain issues, but should not be done lightly as it erases all data. Before formatting, be sure to exhaust other troubleshooting options and back up your data. The formatting process will wipe your Mac clean, so you’ll need to reinstall apps and restore data afterwards. Use formatting as a last resort if you’re experiencing major system issues. Otherwise, try less drastic fixes first. In the end, formatting is a powerful troubleshooting tool but needs to be done carefully.