When using macOS, you certainly know if you’ve opened a Pages file or are editing an email. But, below the surface are files that macOS uses that you don’t see all the activity required for background processes, Time Machine backups, Spotlight indexing, and other system needs. When you want to eject a mounted volume, like a volume on an external SSD or hard drive, you can run afoul of macOS’s hidden needs.

You can try to eject a volume normally in these ways:

• Select it in the Finder and press Command-E
• Select it in the Finder and choose File > Eject
• Control-click/right-click the volume in the Finder and choose Eject

If you’re lucky, when you try to eject a volume, you will see a message with specific details, such as: The disk "My Photos" couldn't be ejected because "Adobe Photoshop 2024" is using it. Quitting Adobe Photoshop will let you eject “My Photos”, but if there’s something happening at a system level, you will see a message worded like this: The disk "My Photos" wasn’t ejected because one or more programs may be using it. You can try to eject the disk again or click Force Eject to eject it immediately. Cancel and Force Eject buttons are part of the dialog, and a progress spinner appears next to the phrase “Trying to eject.”. That does not help resolve the situation. Here’s what you can do to narrow down the problem:

Close Finder windows. As odd as it seems, sometimes merely having a window open in the Finder that shows the contents of the volume or a folder on it may make the Finder believe that a “program” is using that mounted item. Close the Finder window and try again.

Remove the volume from Spotlight. I’ve found that Spotlight can sometimes seize hold of a volume and mark it as unejectable even when indexing isn’t actively in process on that volume. You can check if that’s the problem by going to Apple menu  > System Settings... > Siri & Spotlight, scrolling down to the bottom of the view, and clicking Spotlight Privacy. Drag the volume into the window (or click + and navigate to it, then add it), and click Done. This immediately removes the volume from indexing. Try to eject now. If it works, that was the problem. However, if you want to search items on that volume, you will need to remove it from Spotlight Privacy later.

Check if Time Machine is backing up. If Time Machine is actively backing up the volume, you may be unable to eject it. Check the status of Time Machine either through its system menu or by going to Apple menu  > System Settings... > General > Time Machine. If it’s underway, you can choose Skip This Backup from the Time Machine system menu or click the “x” box next to the active session in the System Settings view and wait for Time Machine to wind down. You can exclude the volume from Time Machine by using the settings view: click Options, click the + (plus) sign at the bottom of Exclude from Backups, and add the volume while mounted. Click Done.

Shut down. For a physically connected external volume, choose Apple menu  > Shut Down. When your Mac is completely shut down, unplug the SSD or HDD. Press the power button on your Mac to start up. For a “logically” mounted volume, such as a disk image or networked volume, choose Apple menu  > Restart. On restart, the volume should be unmounted by default. If not, immediately select it and use an eject option listed above, which should now work.

Apple has increasingly made it hard to mess with macOS system files. That’s true whether you intentionally want to extend macOS’s functionality or if a malicious party is trying to install and activate a virus. However, many system components and all Apple and third-party apps rely on preferences and other files to store your custom settings, caches for work in progress, and other data. If those files corrupt, macOS may be perfectly fine, but you can’t get anything done in an app or your account.

Once you’ve gone through troubleshooting your Mac within your account that doesn’t seem to improve matters, the next big leap before reinstalling macOS is to set up a fresh macOS user account. From this account, you can test hardware, like your Wi-Fi or ethernet adapter; add printers and scanners; or run third-party software that keeps crashing on launch.

Because a fresh account typically contains nothing that would already be corrupted, you can isolate whether a problem is in your everyday user account or a system-wide issue–maybe even hardware related.

Here’s how to set up a fresh, new user account:

• Open "System Settings..." from the  Apple menu

• Go to "Users & Groups"

• Click the "Add User..." button

• Enter your password if prompted

• Choose whether to create a Standard or Administrator account, give it a name, password, and hint, and click "Create User"

When making the account, what kind should it be?

Create a Standard account if you want to test a problem from the perspective of a user without any extra privileges.

Create an Administrator if that’s your normal account type–that’s typical–and you’re trying to perform an apples-to-apples comparison.

• Choose  Apple menu > Log Out [name]

• At the login screen, select the new account, enter the password, and click the arrow to log in

Now you can check if your problem persists.

When you’ve debugged your problem, you can get rid of the account. You must be logged in using an Administrator account to do this.

Your Mac includes a built-in tool called Apple Diagnostics (formerly called Apple Hardware Test). This tool will be handy if you are dealing with a hardware issue and not a software issue. You can use it to find and diagnose issues with your Mac’s internal hardware such as the Wi-Fi hardware, the Bluetooth hardware, Touch ID, the fan, or the power adapter, etc.

Prepare your Mac

• If you can install the latest macOS updates (https://support.apple.com/en-us/108382)
• Disconnect all external devices except keyboard, mouse, display, Ethernet connection and connection to AC power
• Determine if you have an Apple silicon Mac or an Intel Mac, go to the  Apple menu > About This Mac to find out (on a Mac with Apple silicon, About This Mac shows an item labeled Chip, followed by the name of the chip, on an Intel-based Mac, About This Mac shows an item labeled Processor, followed by the name of an Intel processor)
• Shut down your Mac (if you can't shut it down normally, press and hold its power button for up to 10 seconds, until your Mac turns off - every Mac has a power button; on laptop computers that have Touch ID, press and hold the Touch ID button)
• Turn off your Mac, then wait a few seconds for your Mac to completely turn off

On an Apple silicon Mac

• Press and hold the power button on your Mac (on laptop computers that have Touch ID, press and hold Touch ID)

• As you continue to hold the power button, your Mac turns on and loads startup options

• When you see Options, release the power button

• Press and hold Command (⌘)-D on your keyboard until your Mac restarts

On an Intel Mac

• Turn on your Mac, then immediately press and hold the D key on your keyboard as your Mac starts up (if using the D key doesn't work, press and hold Option (⌥)-D at startup instead)

• Release the key when you see a progress bar or you're asked to choose a language

Run Apple Diagnostics

Follow the onscreen instructions, which vary based on your Mac, the version of macOS that it’s using, and whether certain parts of your Mac have been repaired or replaced.

As you follow the onscreen instructions:

• If your Mac isn’t already connected to the internet, you’re asked to choose a Wi-Fi network, or you can use an Ethernet cable to connect to your network

• If asked to review terms and conditions, you might be given the option to run diagnostics offline (in that case, click Run Offline)

• In macOS Tahoe 26 and later, you’re asked to choose a specific diagnostic to run, such as a diagnostic for your built-in display, keyboard, or trackpad; in earlier versions of macOS, this is automatic

When testing is complete, Apple Diagnostics shows the results. If you see one or more reference codes and need more explanation, refer to the list of Apple Diagnostics reference codes (https://support.apple.com/en-us/102334).

If you can't use this information to resolve the issue on your own, you might need service (https://getsupport.apple.com/?caller=kbase). Provide the reference code you receive from the test when taking your Mac to an Apple Authorized Service Provider, Apple Store, or an Independent Repair Provider. Genuine Apple parts are also available for out-of-warranty repairs through Self Service Repair (https://support.apple.com/self-service-repair).

This can be especially helpful if you're pretty certain that your Mac's the problem, not the printer (if your other computers can print just fine). You'll want to use this only as a last resort, though, because you'll have to set up all of your printers and scanners again.

Here's how you do it: 

• Open "System Settings..." from the  Apple menu
• Go to "Printers & Scanners"
• Right or Control click on any listed printer
• Choose "Reset Printing System..." and click "Reset"
• Wait for your Mac to complete the task and after it's finished, click the "Add Printer, Scanner, or Fax..." button to add back your printer(s)

If you hold down the Option (alt) key and click the Wi-Fi icon in the menu bar, it will  provide you with details about your router and the network you're using. The items in gray are all pieces of additional information seen only in this mode.

• IP Address: This is your computer's IP address.

• Router: Your router's IP address. You can type this into your browser to access your router's web interface.

• Security: Your router's security. Most routers on the market offer WPA2 Personal, and it keeps your network encrypted.

• BSSID: This is your router's MAC, or hardware address. It acts as an identifier for your router that lets it talk to other network-connected devices.

• Channel: This is your WLAN channel, and it determines which radio frequency the router uses to transmit information.

• RSSI: Received Signal Strength Indicator measures how well a device "hears" a signal from the router. It's useful for determining if you have enough signal to get a good wireless connection.

• Noise: This measures how much radio noise is interfering with the RSSI signal. Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power, often expressed in decibels.

• TX Rate: The transmit rate is the speed of the data that is transmitted between your router and your computer. Right now I have a speed of 450 Mbps.

• PHY Mode: This is the wireless protocol that the router uses, according to the IEEE 802.11 wireless standard.

• MCS Index: This number corresponds to the protocols uses to encode the radio signal.