How to format a Mac

The Macs are generally considered stable and reliable, are not susceptible to malware as Windows PC (with a few exceptions), and are also less crash. This, however, does not mean that they are perfect or that you do not want to be able to format them to reinstall the operating system from scratch.

With today’s guide, I want to explain how to format a Mac using the recovery function included in macOS, called Recovery, or a USB stick. In both cases it is really a breeze, you just have to create a backup copy of your data (with formatting, in some cases, you could lose the files on the Mac drive) and commit to follow the instructions carefully that I am about to give you.

The tutorial is valid for all the most recent versions of macOS but it also easily adapts to those a little more “dated”, since the steps to be taken are very similar. So, what do you think? Are you ready to start? Well, then roll up your sleeves, take a few minutes of free time and format your Mac by following the instructions below. You’ll do it without any problem, guaranteed!

Preliminary operations

Before even explaining to you, in practice, how to format a Mac , I think it is my duty to advise you to make a backup of your personal data as a preliminary operation, so that you can restore it, if something goes wrong, or to easily transfer it to a new Mac.

In this regard, if you are about to format your old computer to get rid of it and intend to transfer the data to a new Mac, I recommend that you create a backup copy of the data with Time Machine : if you have never heard of it, it is a utility present “standard” in macOS, which allows you to create backup copies of the system (or only certain folders) on an external disk , in a totally automatic way.

If you have already configured Time Machine previously, to update the copy of the archived data, connect the backup disk to the computer, click on the Time Machine icon residing in the Mac menu bar, at the top right (the icon depicting a analog clock ) and select the item Back up now resident in the proposed menu.

Where the icon is not visible, open System Preferences (the gear icon located on the Dock ), click on the Time Machine icon and put the check mark next to Show Time Machine in the toolbar menu .

If you want to exclude one or more folders that you do not deem necessary from the backup, call up the same menu seen previously, click on the item Open Time Machine preferences located inside it, click on the Options button and press the [+] button to choose the items to exclude. When done, click on the Save button and wait for the backup to complete.

If you have never used Time Machine before and need a hand in completing the initial setup, I refer you to my tutorial on how to backup with Time Machine .

If, on the other hand, you intend to format your Mac due to various software problems, I do not recommend using Time Machine, as a subsequent restore of the backup could also return the old problems. In this case, what you can do is manually copy the important data to an external hard drive , after connecting the latter to the computer: if you don’t know how, I invite you to consult my tutorial completely dedicated to the subject .

Together with this, I recommend that you activate data synchronization also on iCloud , in order to have an online copy of photos, e-mails, contacts, calendars, passwords and many other elements closely related to the operating system. However, keep in mind that following this operation, you may need to purchase additional storage space , in order to increase the storage available to you on the platform.

Having clarified this aspect, to enable data synchronization on iCloud, open the System Preferences by clicking on the gear-shaped icon that resides in the Dock bar , click on the Apple ID button located at the top, then on the iCloud item (on the left) and check that the boxes for the items to be synchronized ( iCloud Drive , Photos , Mail , Contacts , Safari , Keychain and so on) are checked , otherwise you can do it.

How to format a Mac without losing data

Once you have secured your personal settings, it is time to get to the heart of this guide and to explain, in practice, how to initialize or reset your computer, using the tools “on board” the Mac.

Let’s start with the procedure to format a Mac without losing data : all you have to do, in this case, is to access the macOS Utilities and choose to reinstall the operating system .

Following this operation, the most up-to-date copy of macOS will be downloaded from the Internet and installed on your computer, without deleting any personal data. This procedure is useful if, for example, you have carried out interventions on the “delicate” files of macOS, perhaps using the Terminal, but obtaining unexpected and unpleasant results.

To start, therefore, turn off the Mac (by clicking on the apple icon located at the top left of the screen and choosing the Shut Down item from the menu that appears) and wait for it to be completely turned off.

Now, if you have a Mac equipped with an Intel processor , turn it on, immediately press the combination of keys cmd + r and keep both keys pressed until the logo of the bitten apple appears on the screen. If, on the other hand, you have a Mac equipped with an Apple Silicon processor , turn it on and continue holding the power button until the boot options window appears ; from there, find the gear icon with the words Options and click on Continue ;

If everything went well, you should be presented with a window in which to select the language to use for the next steps: after this, enter the Mac password , the one you usually use to log in to your profile. If multiple users are configured on your computer, select one of the administrators whose password you remember and enter the password when prompted.

Now, click on the Continue button to display the macOS Utilities window , select the Reinstall macOS item and wait for the analysis of the options relating to the currently installed operating system to be completed. When prompted, click on the Continue button , accept the terms of use of macOS by responding affirmatively to the next warning and, having done this, select the disk on which to reinstall the “new” copy of macOS (generally identified by the wording Macintosh HD ).

At this point, click on the Continue / Install button and, if you have enabled protection through FileVault (the disk encryption system), type the Mac administration password , in order to start the procedure of copying the operating system.

If the necessary files are not available on the Mac, they will have to be downloaded from the Internet; therefore, if you are not yet connected to the network, proceed to do so by clicking on the cleats icon located at the top right and, after selecting the Wi-Fi network to use, enter the relevant access key in the appropriate field. If you prefer, you can also use the wired Ethernet connection , if you have a Mac with this type of input (or a dedicated adapter).

At the end of the installation procedure, the Mac will restart automatically and, the next time you turn it on, you will see the macOS login screen: the problems you had encountered so far should also have been solved.

If you do not have the possibility to connect to the Internet or you need to reset multiple Macs and you do not want to waste time downloading the operating system several times, you can create a USB stick with macOS as explained later in this tutorial.

How to format a Mac before selling it

To format a Mac before selling it or simply to perform a clean installation of the operating system on a computer you intend to keep, you need to completely wipe the contents of the disk , so that your data is safely deleted and unrecoverable.

To do this, open the macOS Utilities as I indicated in the previous chapter of this guide, click on the Disk Utility option and then on the Continue button , located at the bottom. Now, select the disk on which macOS is installed (eg Macintosh HD ), click on the Initialize button located at the top and wait for the disk formatting panel to appear.

When this happens, type the name to assign to the drive in the appropriate field and make sure that the APFS option is selected in the Format drop-down menu . If you are using a version of macOS older than 10.13 High Sierra and therefore not compatible with APFS, you must select the options macOS extended (journaled) and Partition GUID map from the Format and Scheme drop-down menus .

Now, press the Initialize and Finish buttons to start formatting the disk, which will result in the deletion of all data already present . If necessary, repeat the same operation for the data partition and for any other disks in the computer.

If you want to be sure that the data currently on the Mac disk is unrecoverable, even using programs suitable for the purpose , click on the Security Options button and set the degree of security you prefer from the menu that is proposed (the more writes you choose, the deletion will be safe, but also the drive formatting procedure will be slower).

Please note that, on the most recent editions of macOS (from Catalina onwards), you can format the entire disk (including the data partition) in one go, if this has been organized in the form of an APFS volume group : to do so , click on the Initialize Volume Group button and wait for the complete data deletion to be completed.

Once the data on all the disks have been deleted, return to the macOS Utilities home screen, choose the Install macOS option and, after clicking the Continue button , accept the operating system conditions of use. Finally, select the disk you previously formatted (eg Macintosh HD) and click on the Install button to start the operating system installation procedure. If required, connect to the Internet using the Wi-Fi icon at the top right (or an Ethernet cable, if your Mac has the appropriate port or if you have an adapter).

The installation phase of the operating system may take a long time, as all the necessary files, in this case, are downloaded from the Internet. At the next reboot, you will be asked to perform the first macOS configuration procedure : since it is your intention to get rid of the computer, turn off the computer and let the new owner do it.

In case of second thoughts, if you want to continue to keep the Mac for you even if it has been formatted, follow the instructions provided on the screen to configure macOS: choose your country , the keyboard layout and the dictation language to use, connected to the wireless network that you prefer and accept the terms of use of the operating system. Now, indicate whether to restore your computer from an existing data backup by transferring it from another Mac, from a Time Machine backup (you will need to insert the backup disk when prompted), from a startup disk or from a Windows computer, or whether to continue setting up your Mac without transferring data .

Now, choose whether or not to log in with an Apple ID , indicate the settings related to the user account and finally specify whether or not to send the usage statistics to Apple and / or third-party developers, configure Usage Time and Siri and select the graphic theme to use. Finally, click on the Continue button for the last time and wait for the Mac desktop to appear on the screen.

If you do not have the possibility to connect to the Internet and, consequently, to recover the files necessary for the reinstallation of macOS, or you need to format multiple Macs and do not want to waste time downloading the operating system from the Internet several times, you can create a USB stick with macOS and use it to format the Mac. You will find everything explained in the next chapter of this guide.

How to format an old Mac

Do you need to format an old Mac or do you need to format one or more recent Macs and don’t have the ability to download macOS directly from the Internet? If so, you can create a USB stick with the operating system installation files and use that to format your computer and reinstall macOS.

To succeed in this intent, you can directly use the macOS Terminal (recommended) or a third-party application, easier to use but which could give some problems with the latest versions of the Apple operating system, called Install Disk Creator .

In any case, keep in mind two fundamental aspects: if you need macOS 10.13 or later editions , since the download will take place via the Mac App Store , it is essential that the “second” computer (the one from which you are preparing to make the USB stick) is associated with an Apple ID already used on the old Mac, otherwise the operating system will not be available.

In this regard, you can safely create a new user on the computer (by going to System Preferences> Users and Groups ) and set the Apple ID in question . This step is not necessary for the download of the operating systems macOS Sierra 10.12, macOS El Capitan 10.11 and macOS Yosemite 10.10, as Apple provides the “direct” download links for the operating system files.

Secondly, the USB key to be used for the purpose must necessarily be empty and have a capacity of at least 12 GB ; if you do not have one, feel free to consult my purchase guide dedicated to pendrives , so as to receive valuable advice in this regard. If your computer only has USB-C ports, however, you need to opt for a key with this connector or, alternatively, a USB-A to USB-C adapter / hub .


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Once you have everything you need, proceed as follows: first, on the dedicated support page on the Apple website, locate the macOS version of your interest from the Download macOS paragraph and click on the relevant link, to start downloading the package .dmg containing the operating system; for the most recent editions of Mac (10.13 High Sierra, 10.14 Mojave and 10.15 Catalina) the Mac App Store will open instead : to start the file download, click on the Get and Download buttons and, if necessary, type in your account password Apple (or authorize everything via Touch ID, if your computer supports its use).

When the download is complete, if the file was obtained through the app store, interrupt the installation process of the operating system, by right-clicking on the icon that appears in the Dock bar and then clicking on the item Exit , attached to the menu that appears, or by pressing the Exit button located in the warning window that appears (the one relating to the incompatibility of macOS on a more recent edition of the operating system).

At this point, to proceed from Terminal , open the latter (located in the Other folder of the Launchpad ) and give the command sudo /Applications/Install\ macOS\ Big\ –volume /Volumes/pendrive(where instead of macOS \ Big \ you must enter the name of the installer of the version of macOS that you intend to install, putting the symbol “\” before each space, and instead of pendrive you must enter the name of the key you intend to use). Then type in the Mac administration password , and press Y to confirm. The key will clearly be formatted.

If you prefer to use the Install Disk Creator utility , go to its website , click on the Download the macOS app button and, once the program has been downloaded, connect the USB key to your computer and copy the file obtained in the MacOS Applications folder . To run Install Disk Creator, double click on the newly created icon and press the Open button .

Once the software has been started, if you have downloaded macOS from the App Store, the relative installation package should be recognized automatically; otherwise, click on the Choose a macOS Installer … button located at the top and select the .dmg package you obtained earlier.

We are almost there: now use the drop-down menu Select the volume to become the installer to select the USB key and, bearing in mind that the operation will delete all the data on the latter, click on the Create installer and Erase disk buttons , to start creating the drive (which may take some time).

Once the key has been created (regardless of the method used to copy macOS to it), connect it to the Mac to be formatted, turn on the latter and, during startup, hold down the alt button on the keyboard, until the menu for the selection of the boot disk .

Now, you just have to double click on the icon of the installer of the operating system of your interest and wait for the appearance of the macOS Utilities ; From now on, you can follow the directions I gave you in the chapters on how to format your Mac without losing data and how to format a Mac before selling it , depending on whether you want to keep personal data on your computer or not.

How to format a MacBook

You don’t have a desktop computer from the Apple line but you have a laptop and, for this reason, would you need to understand how to format a MacBook ? In this regard, you will be pleased to know that the steps to be taken, in the various cases, are identical to those seen for “desktop” Macs: for this reason, I refer you to reading the previous chapters of this guide, to clarify indications on what to do.


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