Your MacBook Air from 2015 is running slow, acting strange, or you're getting ready to sell it. Whatever the reason, you've landed on the exact process: how to factory reset MacBook Air 2015. It's a straightforward procedure, but there are a few gotchas that can trip you up if you're not careful.
According to Apple's support documentation, the 2015 MacBook Air (model A1466) supports up to macOS Big Sur (11.x) as its final officially supported operating system. That matters because the version of macOS you reinstall determines which key combination you'll use to start the reset. Our editorial approach here is grounded in official Apple guidance and verified user reports, not guesswork.
Let's walk through the whole thing step by step, starting with what a factory reset actually does to your machine.
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Quick Answer
Hold Command+R as the Mac boots. Open Disk Utility. Select the internal drive.
Click Erase and choose Mac OS Extended format. Quit Disk Utility. Choose Reinstall macOS.
Follow the prompts. Your Mac restarts to a clean setup screen. The whole process takes 1 to 3 hours.
What a Factory Reset Actually Does to a 2015 MacBook Air
A factory reset is a two-step process. First, you erase the storage drive. Then you install a fresh copy of macOS.
The result is a Mac that looks and behaves exactly like it did the day you unboxed it.
Here's what gets wiped:
- All your personal files, photos, music, and documents
- Every application you've installed
- Your system settings, preferences, and customizations
- User accounts, passwords, and saved network credentials
- Browser history, cookies, and cached data
- Login keychains and saved passwords
Here's what does NOT get erased:
- The firmware or EFI settings
- The hardware serial number and board identifiers
- The original macOS Recovery partition (unless you deliberately wipe it)
- The internal clock and NVRAM settings (those are reset separately)
Important distinction for the 2015 model. Unlike newer Macs with Apple Silicon or the T2 chip, the 2015 MacBook Air does not have an "Erase All Content and Settings" button in System Preferences. That feature only exists on Macs from 2018 and later. For the 2015 model, you do this the old-fashioned way through macOS Recovery.
Why you'd want to do this:
- Selling or gifting the Mac: removes all personal data so the next owner starts fresh
- Persistent software issues: fixes corruption, kernel panics, and slowdowns
- Preparing for trade-in: many programs require a wiped, clean-installed OS
- Removing malware or adware: some infections embed deep enough that only a full erase removes them
- Starting over with a clean slate: sometimes you just want that "new Mac" feeling
The one thing to know before you start. The 2015 MacBook Air uses a PCIe-based SSD that is proprietary. You cannot swap the drive for a larger one easily. The erase is permanent on this hardware.
Make absolutely sure you have your backups before you proceed.
The Pre-Reset Checklist – Backups, Passwords, and iCloud Sign-Out
This is the step people skip. Then they panic. Don't be that person.
Before you touch a single key combination, run through this checklist. It takes about 15 minutes and saves you hours of regret.
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Step 1: Back up everything you want to keep
You have three good options for backing up a 2015 MacBook Air:
Time Machine (easiest). Plug in an external drive. Open System Preferences. Select Time Machine.
Choose the drive and turn it on. It creates a full backup including apps, settings, and files. The first backup can take a few hours depending on how much data you have.
Let it run overnight.
Manual copy (selective). Drag your important folders to an external drive. This is faster but you lose app settings and system preferences. Good for a quick sale, not great if you plan to restore later.
Cloud backup (convenient but slow). Upload critical files to iCloud Drive, Dropbox, or Google Drive. The 2015 MacBook Air has USB 3.0 and Thunderbolt 2, so local backup is usually faster. Only use cloud for documents you absolutely need.
Our recommendation. Use Time Machine if you think you might want to restore your old setup. Use a manual copy if you're selling the Mac. Either way, verify the backup actually opens before you erase the drive.
Step 2: Sign out of iCloud
This is the most critical step. If you skip it, the next owner cannot activate the Mac. It's called Activation Lock and it's tied to your Apple ID.
Here's how:
- Click the Apple menu. Go to System Preferences. Click Apple ID or iCloud.
- Scroll to the bottom. Click "Sign Out."
- Uncheck everything if you're selling it. Click "Keep Copy" or "Remove from Mac."
- Enter your Apple ID password to confirm.
- Wait for the sign-out to complete.
What if you're on an older macOS version? On OS X Yosemite or El Capitan, the sign-out is in the same place but the interface looks different. Find the "Sign Out" button at the bottom of the iCloud preferences pane.
Step 3: Sign out of iTunes and the App Store
Open iTunes. Go to Account. Choose Authorizations.
Select Deauthorize This Computer. Then sign out in the Store menu.
For the App Store, open the App Store app. Click Store in the menu bar. Choose Sign Out.
Step 4: Disable Find My Mac
Signing out of iCloud typically disables Find My Mac. Check explicitly. Go to System Preferences.
Select Apple ID. Click iCloud. Make sure Find My Mac shows as Off.
If it's still on, click the checkbox and enter your password.
Step 5: If you use FileVault, write down the recovery key
FileVault encrypts your entire drive. When you erase the drive, the encryption key is destroyed. That's fine for the erase itself.
But if you're backing up first, you need the FileVault password to mount the drive in Disk Utility.
Open System Preferences. Go to Security and Privacy. Click FileVault.
If it's on, click "Turn Off FileVault" to decrypt the drive before backing up. This can take hours on a larger drive. Plan accordingly.
If you can't turn off FileVault. Write down the recovery key. It's a long string of numbers and letters. You'll need it during the reset process.
Step 6: Gather your Apple ID and passwords
You need your Apple ID email and password after the reset to reinstall macOS. The installer downloads from Apple's servers. If you don't know your Apple ID password, reset it now at iforgot.apple.com.
Do not start the reset until you have it.
Step 7: (Optional) Unpair Bluetooth devices
If you have an Apple Watch, Magic Mouse, Magic Keyboard, or AirPods paired to this Mac, unpair them. Go to System Preferences. Click Bluetooth.
Find each device and click the X or "Forget." It prevents confusion for the next owner.
When you're done. You should have a recent backup, a signed-out Apple ID, a disabled Find My Mac, and a known Apple ID password. If any of these are missing, go back and fix it.
Which Recovery Method Should You Use? The Decision Tree
This is where most guides go wrong. They tell you one method and leave you stranded when it doesn't work. The 2015 MacBook Air has four different recovery paths.
The right one depends on your specific situation.
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Branch 1: Local Recovery (Command+R) – Fastest Option
Best for: Most people with a working Mac that still boots to the desktop or shows the Apple logo.
What it does: Boots into the recovery partition on your internal SSD. No internet connection required. You can erase the drive and reinstall the same version of macOS that's currently installed.
How to use it:
- Restart your MacBook Air.
- Immediately hold Command and R until the Apple logo appears.
- Release the keys when you see the macOS Utilities window.
The catch. If your recovery partition is damaged or missing, this method either fails to boot or shows a prohibitory sign. This happens more often than you'd think on older Macs.
How to check. After pressing Command+R, watch the screen. If you see the Apple logo and a progress bar, you're in. If you see a flashing folder with a question mark, your recovery partition is gone.
Move to Branch 2.
Branch 2: Internet Recovery (Command+Option+R) – Latest Compatible macOS
Best for: When Local Recovery fails, when you want to install a newer macOS version, or when you're starting from a completely blank drive.
What it does: Downloads a recovery system from Apple's servers over the internet. Then downloads the latest macOS your 2015 MacBook Air supports (macOS Big Sur 11.x as of 2026).
How to use it:
- Restart your MacBook Air.
- Immediately hold Command, Option, and R.
- Keep holding until you see a spinning globe with "Starting Internet Recovery."
- Wait for the download. It can take 30 minutes to several hours.
- You'll eventually see the macOS Utilities window.
What you need. A stable internet connection. The 2015 MacBook Air has WiFi 802.11ac. If your WiFi is flaky, use a wired connection with a USB to Ethernet adapter.
How long it takes. The recovery system is about 1.5 GB. The full macOS installer is about 6 GB. On a 50 Mbps connection, expect about 2 hours.
On a slower connection, plan for 4 hours or more.
The catch. If your MacBook Air has a firmware password set, Internet Recovery will ask for it before proceeding. If you don't know the password, you're stuck.
Branch 3: Original macOS Recovery (Shift+Option+Command+R) – For Sale or Legacy Needs
Best for: When you want to install the original macOS that shipped with the 2015 MacBook Air (OS X Yosemite or El Capitan).
What it does: Downloads the version of macOS that came with your specific MacBook Air model.
How to use it:
- Restart your MacBook Air.
- Immediately hold Shift, Option, Command, and R.
- Wait for the spinning globe.
- The installer downloads the original OS.
Important note. The original OS is very old. Many current apps and browsers won't work on it. Use Branch 2 unless you have a specific reason to install the original version.
Branch 4: Bootable USB Installer – When Recovery Partitions Are Gone
Best for: When none of the above methods work, when you have a damaged recovery partition AND a slow internet connection, or when you want to install macOS from a local source.
What it does: A USB drive with a macOS installer on it. You create it on another Mac, then plug it into your 2015 MacBook Air and boot from it.
How to create one (on another Mac):
- Download the macOS installer from the App Store.
- Plug in a 16 GB or larger USB drive.
- Open Terminal and run:
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume - Wait for the process to finish (about 15-20 minutes).
- Eject the USB drive safely.
How to boot from it:
- Plug the USB drive into your 2015 MacBook Air.
- Restart and hold the Option key.
- Select the yellow USB installer icon.
- Press Enter.
The big advantage. You control the timing. No waiting for downloads. No reliance on Apple's servers.
The big disadvantage. You need a second Mac to create the installer. If you don't have access to another Mac, this method won't work.
Decision Summary Table
| Condition | Best Method | Time Required | Internet Required |
|---|---|---|---|
| Working recovery partition | Command+R | 30-60 minutes | No |
| Damaged recovery partition | Command+Option+R | 2-4 hours | Yes |
| Want original OS | Shift+Option+Command+R | 2-4 hours | Yes |
| No internet, no recovery | Bootable USB | 15 min (USB) + 30-60 min (install) | Only for USB creation |
| Blank drive, no other Mac | Command+Option+R | 2-4 hours | Yes |
| Firmware password set | Must remove password first | Varies | Depends on method |
Erasing the Drive in Disk Utility – What to Click and What to Avoid
This is the moment of no return. Once you erase the drive, your data is gone.
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Opening Disk Utility
From the macOS Utilities window, click "Disk Utility" and then click Continue. You'll see a window with a sidebar on the left and details on the right.
The most important setting: Show All Devices
By default, Disk Utility hides the physical drive and only shows the volumes. You need to see the actual drive. In the menu bar, click View.
Select Show All Devices. The sidebar now changes to show the physical drive at the top level.
For the 2015 MacBook Air, you'll see something like this:
- Apple SSD SM0128G Media (the physical SSD)
, Container disk1 (if using APFS format)
, Macintosh HD (the main volume)
, Macintosh HD, Data (if using APFS with separate data volume)
Or on older macOS versions:
- APPLE SSD SM0128G Media
, Macintosh HD (the main volume)
What to erase
Select the top-level physical drive. The one with the model name like "Apple SSD SM0128G Media." Do NOT select "Macintosh HD" or any sub-volume. You want to erase the entire drive, not just the partition.
Click the "Erase" button in the toolbar.
Format: APFS or Mac OS Extended?
This is a common point of confusion. Here's the simple rule:
If you're installing macOS Big Sur or later: Use APFS. Big Sur requires APFS for the boot drive. APFS is faster and more reliable.
If you're installing macOS Catalina or earlier: Use Mac OS Extended (Journaled). Older macOS versions don't support APFS as a boot volume.
The 2015 MacBook Air can use either. The SSD is compatible with both formats. APFS is the modern choice. Mac OS Extended is the safe choice for an older OS.
Scheme: GUID Partition Map
Below the format field, there's a "Scheme" dropdown. It defaults to "GUID Partition Map." Leave it there. The other options are for PowerPC Macs and Windows boot drives.
Your 2015 MacBook Air needs GUID Partition Map.
Security Options
Click "Security Options" in the Erase dialog. You'll see a slider with four levels:
| Level | What it does | Time | Use case |
|---|---|---|---|
| Fastest | Wipes file system metadata, marks space as available | 1-2 seconds | Normal use, selling to a friend |
| Second level | Single pass of zeros over free space | 30-60 minutes | Slightly more secure |
| Third level | 3-pass wipe (DoD 5220.22-M standard) | 2-3 hours | Sensitive data |
| Most secure | 7-pass wipe | 5-8 hours | Government-level paranoia |
The truth about SSDs and secure erase. The 2015 MacBook Air uses a solid-state drive. SSDs handle data differently. The built-in TRIM command makes traditional passes less effective.
The fastest option is actually very secure for SSDs because the drive's controller handles data sanitization internally.
Our recommendation. For most people, the fastest option is fine. If you're selling the Mac or have sensitive data, encrypt the drive with FileVault first, then do a fast erase. The encryption key is destroyed and the data becomes unreadable.
The actual erase
After selecting the format and scheme, click "Erase." A progress bar appears. It should complete in under 10 seconds. If it takes longer, something is wrong.
When it finishes, you'll see "Erase process has completed." Click Done. Close Disk Utility.
What if the erase fails?
Error: "Erase process has failed." This usually means bad blocks or a failing SSD controller. Try running First Aid from Disk Utility first. If First Aid reports errors, the SSD may be failing.
The 2015 MacBook Air is old enough that SSD failure is a real possibility.
Error: "MediaKit reports not enough space." This happens with a partition map issue. Go back to View. Select Show All Devices.
Select the physical drive. Try the Erase again. If it still fails, restart into Recovery and try again.
Error: "Could not unmount disk." Something is still using the drive. This is rare in Recovery mode. Restart and try again.
Reinstalling macOS on the 2015 MacBook Air – Step by Step
You've erased the drive. Now you need to put an operating system back on it.
Starting the installation
From the macOS Utilities window, click "Reinstall macOS" or "Reinstall macOS Big Sur." Click Continue.
The installer walkthrough
Step 1: Agree to the terms. You'll see the software license agreement. Click Agree. A pop-up asks you to confirm.
Click Agree again.
Step 2: Select the destination disk. You'll see one option: "Macintosh HD" or "Untitled." Select it and click Continue.
Step 3: Wait for the download. This is the long part. The file is about 6 GB for Big Sur. A progress bar shows "Downloading additional components." The estimated time is usually wrong.
Don't trust it. Just let it run.
What if the download fails? It happens. If the download fails, the installer shows an error. Click Cancel.
Restart the Mac. Try again. If it fails repeatedly, switch to the Bootable USB method.
Step 4: The installation begins. After the download completes, the Mac restarts automatically. You'll see the Apple logo and a progress bar. This takes 20 to 40 minutes.
During the installation, the Mac may restart multiple times. This is normal. Do not interrupt it. Do not close the lid.
Do not press any keys.
Step 5: The Setup Assistant. When the installation completes, the Mac restarts one more time. You'll see the Setup Assistant screen. It asks you to:
- Select your country or region
- Choose a keyboard layout
- Connect to WiFi
- Sign in with your Apple ID (optional)
- Create a local user account
- Choose whether to enable FileVault
If you're selling the Mac: Press Command+Q to quit the Setup Assistant. Then shut down. The new owner completes the setup themselves.
If you're keeping the Mac: Go through the setup normally. Create a new user account. Sign in with your Apple ID.
Enable FileVault if you want it.
Restoring from Time Machine
If you backed up with Time Machine:
- Complete the Setup Assistant to reach the desktop.
- Connect your Time Machine backup drive.
- Open Migration Assistant (Applications > Utilities > Migration Assistant).
- Select "From a Mac, Time Machine backup, or startup disk."
- Select your backup drive.
- Choose what to restore.
- Wait for the restore to complete.
The restore can take several hours. The 2015 MacBook Air's USB 3.0 ports handle it well.
What if you don't want to restore?
You're done. The Mac is clean. Install your apps fresh.
Copy your files from the manual backup. This is the "new Mac" feeling.
What if the installation hangs?
The progress bar stops for more than 30 minutes. Wait first. Some installations pause. If it's been over an hour with no movement, force restart by holding the power button for 10 seconds.
Try the installation again.
The installer shows "macOS could not be installed on your computer." This usually means the drive is incompatible with the macOS version. Make sure your 2015 MacBook Air supports the version. Big Sur is the latest supported as of 2026.
The Mac boots to a blank screen. This is rare. Restart and hold Command+R to get back into Recovery. Run Disk Utility's First Aid on the drive.
Try the installation again.
Post-installation checklist
- Mac boots to the desktop or Setup Assistant
- WiFi works
- Sound works
- Keyboard and trackpad are responsive
- Display brightness controls work
- Battery status shows correctly
- USB ports recognize devices
- About This Mac shows the correct model and macOS version
If any of these don't work, reset NVRAM (Command+Option+P+R at startup) or the SMC.
One last thing. As of 2026, the 2015 MacBook Air is considered vintage by Apple. Big Sur is the end of the line for official support. It works great for browsing, email, documents, and light media.
It is not suitable for modern gaming or heavy video editing.
Mistakes That Ruin the Reset – Activation Lock, FileVault, and Firmware Passwords
Three specific issues stop people cold. Let's cover each one.
Activation Lock – The brick you create by skipping iCloud sign-out
This is the most common mistake. You erase the drive, reinstall macOS, and hand the Mac to the new owner. They boot it up, connect to WiFi, and see a message: "This Mac is linked to an Apple ID."
You've just given them a brick.
How it happens. Activation Lock is tied to Find My Mac. When you erase the drive without signing out of iCloud first, the Mac's serial number stays registered to your Apple ID on Apple's servers. The new owner cannot bypass this.
How to fix it (before the reset). Sign out of iCloud. Verify that Find My Mac shows as Off. If you've already erased the drive, go to iCloud.com.
Log in. Go to Find iPhone. Select your MacBook Air from the device list.
Click "Remove from Account." This deactivates Activation Lock remotely.
If you can't remember your Apple ID password. Go to iforgot.apple.com before you erase anything. Reset the password. Then sign out of iCloud on the Mac.
What happens if you sell it and forget. The buyer contacts you. You log into iCloud.com and remove the device. If you're unreachable, the buyer is stuck.
Apple's support won't remove Activation Lock without proof of purchase.
FileVault – The encrypted wall you might hit
FileVault encrypts your entire SSD. It's good for security. It's bad for factory resets if you forget the password.
The problem. When you boot into Recovery mode and open Disk Utility, the drive shows as locked. You can't erase it without unlocking it first. Disk Utility prompts for the FileVault password.
If you know the password. Enter it. The drive unlocks. Then erase it normally.
The erase destroys the encryption key. You don't need to decrypt the drive first.
If you don't know the password. You need the recovery key. If you lost that too, the data is permanently encrypted. You can still erase the drive by selecting it and clicking Erase anyway.
You'll lose everything with no chance of recovery. That's fine if you've already backed up.
Firmware Password – The lock you didn't know existed
A firmware password (EFI password) prevents your Mac from booting from any drive other than the internal one. It also blocks Recovery mode and Internet Recovery.
How to check. Restart the Mac and hold Command+R. If you see a lock icon asking for a password, you have a firmware password.
If you know the password. Enter it. You'll get into Recovery normally. The firmware password does not prevent the factory reset itself.
If you don't know the password. You cannot factory reset the Mac. The only ways to remove a forgotten firmware password are:
- Take it to an Apple Store or Apple Authorized Service Provider. You need proof of purchase.
- Contact the previous owner if you bought it used.
Other mistakes to avoid
Skipping the backup. Do it. We've seen too many people who lost years of photos.
Choosing the wrong format. APFS for Big Sur and later. Mac OS Extended for older versions.
Erasing the wrong disk. If you have external drives connected, Disk Utility shows them too. Double-check you're erasing the internal SSD.
Interrupting the installation. The Mac restarts multiple times. This is normal. Do not force shutdown.
Forgetting to deauthorize iTunes. If you sell the Mac without deauthorizing, you lose one of your five authorized computers for your Apple ID.
Not updating after the reset. Run Software Update after the clean install. Install all available security patches.
After the Reset – Handing It Off or Setting It Up Fresh
You've erased the drive. You've reinstalled macOS. The Mac restarts to the Setup Assistant.
Now what you do depends on whether you're keeping it or passing it on.
If you're selling or giving away the Mac
Stop at the Setup Assistant. When the Mac reaches the "Welcome" screen, press Command+Q to quit. A dialog appears: "Are you sure you want to shut down your Mac?" Click Shut Down.
That's it. The Mac is ready for the new owner. They turn it on, see the Setup Assistant, and go through the initial setup themselves.
Do not create a test account. This confuses the new owner. Better to leave it at the Setup Assistant.
Include these things. The original power adapter (MagSafe 2 for the 2015 model). A note explaining the Mac is wiped and ready to set up.
What about the previous owner's data. The drive is erased. The data is gone. If you're extremely paranoid, enable FileVault on the fresh installation, then erase the drive again.
This is overkill for 99% of people.
If you're keeping the Mac
Go through the Setup Assistant normally. Select your country, keyboard layout, and language. Connect to WiFi. Sign in with your Apple ID or skip it by clicking "Set Up Later."
Create your user account. Choose a username and password. This becomes the administrator account. Write down the password somewhere safe.
Restore your data. If you used Time Machine, connect the backup drive now. The Setup Assistant detects it and asks if you want to migrate data. If you skipped that, open Migration Assistant later from Applications > Utilities.
Install your apps. Download fresh copies. Fresh installs are cleaner and avoid stale preferences.
Run Software Update. Open System Preferences. Click Software Update. Install any available updates.
This can take another 30 minutes.
Enable FileVault if you want it. Go to System Preferences. Click Security and Privacy. Click FileVault.
Click Turn On FileVault.
Set up iCloud. Sign in with your Apple ID. Enable the services you want: iCloud Drive, Photos, Contacts, Calendars, Find My Mac.
Performance after the reset
A fresh installation of macOS Big Sur runs well on the 2015 MacBook Air. The 1.6 GHz dual-core i5 or 2.2 GHz i7 processor handles basic tasks. The 4 GB or 8 GB of RAM is the real bottleneck.
With 4 GB of RAM. The Mac feels snappy for the first few days. As you install more apps and open more browser tabs, it slows down. Big Sur needs about 2 GB just for the OS.
That leaves 2 GB for everything else. Expect some lag with multiple apps open.
With 8 GB of RAM. Much better. The Mac can handle a dozen browser tabs, a word processor, email, and music playback simultaneously. The 2015 MacBook Air with 8 GB is the configuration to look for if you're buying used.
Battery life after the reset. A fresh OS can temporarily improve battery life. Background processes are gone. But the 2015 MacBook Air's battery is now a decade old.
Apple's original spec was 12 hours of wireless web. As of 2026, expect 4 to 6 hours on a healthy battery. If you get less than 3 hours, the battery may need replacement.
What to do if the Mac runs slowly after the reset
A factory reset usually fixes slowness. If your 2015 MacBook Air is still slow after a clean install, the problem is hardware.
Check Activity Monitor. Open Applications > Utilities > Activity Monitor. Look at the CPU and Memory tabs. If CPU usage is high with nothing running, a background process is misbehaving.
If memory pressure is high, you're running out of RAM.
The SSD might be failing. The 2015 model's SSD is proprietary but replaceable. If the drive has developed bad blocks, the Mac feels sluggish. Run Disk Utility's First Aid.
If it reports errors, the SSD needs replacement.
The thermal paste may have dried out. After ten years, the thermal paste between the CPU and heat sink can degrade. The CPU throttles to avoid overheating. This requires opening the Mac and replacing the paste.
It's not a beginner repair.
Battery swelling. If your MacBook Air sits unevenly on a flat surface, the battery may be swelling. This is a fire risk. Stop using the Mac and take it to a repair shop.
Frequently Asked Questions
How long does a factory reset take on a 2015 MacBook Air?
The erase step takes about 10 seconds. The macOS download takes 20 minutes to 2 hours. The installation takes 20 to 40 minutes.
Total time is usually 1 to 3 hours. A slow internet connection can push it to 5 hours.
Will a factory reset delete everything on my Mac?
Yes. The erase step removes all files, apps, settings, and user accounts. The only thing that remains is the macOS installation you put back on it.
This is why backing up before starting is essential.
Do I need a password to factory reset my MacBook Air?
You need your admin password to sign out of iCloud before the reset. You don't need a password to erase the drive. You need your Apple ID password to sign back in after the clean install.
If FileVault is enabled, you need that password too.
Can I factory reset without a recovery partition?
Yes. Use Internet Recovery by holding Command+Option+R at startup. This downloads the recovery system from Apple's servers.
If you don't have internet access, create a bootable USB installer on another Mac.
What macOS version should I install on my 2015 MacBook Air?
The latest officially supported version is macOS Big Sur (11.x). You can also install Catalina (10.15) or Mojave (10.14) for older software compatibility. The original shipped OS was OS X Yosemite or El Capitan.
Stick with Big Sur for the best security and performance balance.
How do I completely wipe my MacBook Air before selling it?
Follow the full process in this guide. Backup your data. Sign out of iCloud and disable Find My Mac.
Boot into Recovery. Open Disk Utility and erase the entire drive. Reinstall macOS.
Quit the Setup Assistant with Command+Q and shut down.
What if the new owner can't activate the Mac?
Activation Lock is the likely cause. Log into iCloud.com. Go to Find iPhone.
Select the Mac from your device list. Click Remove from Account. If you already sold the Mac, contact the buyer and ask for the serial number.
Remove it from your account immediately.
Can I downgrade to an older macOS version?
Yes, but it takes extra steps. You need a bootable USB installer for the older macOS version. The 2015 MacBook Air supports all versions from OS X Yosemite through macOS Big Sur.
You cannot install anything older than Yosemite or newer than Big Sur without a patcher tool.
Why does my Mac show a prohibited sign after the reset?
The prohibited sign means your Mac cannot find a bootable operating system. The most common cause is selecting the wrong format during the erase step. Boot back into Recovery.
Run Disk Utility. Check that the drive is formatted as APFS (for Big Sur) or Mac OS Extended (for Catalina or earlier). Reinstall macOS from scratch.
What should I do if the reset fails halfway through?
Force restart by holding the power button for 10 seconds. Boot back into Recovery. Run Disk Utility's First Aid on the internal drive.
If the drive passes, try the installation again. If First Aid reports errors, the SSD may be failing. Consider replacing the drive before attempting another installation.
For reliable guidance, our editorial policy ensures all information here is thoroughly researched and verified. If you have specific questions about your situation, you can reach us through the contact page. Please understand that while we strive for accuracy, this guide comes with our standard disclaimer regarding user responsibility for data backup and device safety.