"When installing macOS, you may see a list of recently used apps that are 32-bit. You can review this list before deciding to continue installation. You may also see a prohibitory symbol over the icon of each 32-bit app in the Finder, letting you know that the app will not open.

For all 32-bit apps, please contact the developer of the app to learn whether an updated version of their software is available or planned."

"Starting with macOS Catalina, your Mac uses zsh as the default login shell and interactive shell. You can make zsh the default in earlier versions of macOS as well."

"Guided Access limits your device to a single app
and lets you control which features are available.
You can turn on Guided Access when you let a child use your device,
or when accidental gestures might distract you."

"You might get this error when you try to use your scanner from within Image Capture, Preview, or Printers & Scanners preferences.

When attempting to connect to your scanner and begin a scan, you might get a message that you do not have permission to open the application, followed by the name of your scanner driver. The message says to contact your computer or network administrator for assistance, or indicates that your Mac failed to open a connection to the device (-21345).

To resolve this issue, please install the latest macOS updates."

"Some Mac computers can conserve energy using the standby feature.
When your Mac goes into standby mode, it saves your current session
- your open applications, files, and windows - to your hard drive.
Your Mac also turns off some of its hardware systems to save power.

If you have a Mac notebook, standby lets it stay asleep on battery power longer.
A notebook with a fully charged battery can remain in standby mode for up to thirty days
without being plugged in to power.

Mac computers from 2013 or later enter standby after being in sleep mode for 3 hours.
Earlier models enter standby after just over an hour of sleep."

Mac models that can use standby
• MacBook (2015 and later)
• MacBook Pro (2012 and later)
• MacBook Air (2010 and later)
• SSD and Fusion drive versions of Mac mini (2012 and later)
• SSD and Fusion drive versions of iMac (2012 and later)
• Mac Pro (Late 2013)

"This option is available for macOS Mojave, High Sierra, and Sierra after installing security updates."

"... security updates in macOS Mojave 10.14.5 to protect against speculative execution vulnerabilities in Intel CPUs...
macOS 10.14.5 includes security updates for Safari, and the option to enable full mitigation...
Security Update 2019-003 High Sierra & Security Update 2019-003 Sierra include the option to enable full mitigation."

• How to download apps for Mac.
• How to find apps that you bought.
• If you can't find the App Store.
• If you have an issue when you download apps.
• Get help with an app that does not work.

"Starting with iOS 13, IPsec supports HMAC-SHA-256 with IKEv1 VPN.
To make sure that your iOS 13 and macOS Catalina clients can connect to your IKEv1 or VPN server, configure the server to truncate the output of the SHA-256 hash to 128 bits. Truncating to a smaller number of bits might cause the server to drop data that VPN clients transmit."

• MacBook Pro (14-inch, 2023) or MacBook Pro (16-inch, 2023)
• Mac mini (2023)
• Mac Studio (2023)
• Mac Pro (2023)
• iPhone 15 Pro or iPhone 15 Pro Max
• iPad Pro 11-inch (4th generation) or iPad Pro 12.9 inch (6th generation)

"Make sure that all routers on your network use the same name for every band they support. If you give your 2.4GHz, 5GHz, or 6GHz bands different names, devices might not connect reliably to your network, to all routers on your network, or to all available bands of your routers. If your router is providing a Wi-Fi 6E network that isn't using the same name for all bands, Apple devices that support Wi-Fi 6E will identify the network as having limited compatibility."

• What's Bluetooth?
• Find out if your Mac has Bluetooth.
• About Bluetooth menu bar icons.
• Pair your Mac with a Bluetooth device.
• Remove a Bluetooth device from your Mac.
• Connect to Bluetooth devices after wake or startup.
• Wake your computer with Bluetooth devices.
• Connect multiple Bluetooth devices to one computer.
• Fix interference from other household devices.
• Press startup keys on a Bluetooth keyboard.

In ongoing efforts to improve web security for our users, Apple is reducing the maximum allowed lifetimes of TLS server certificates. TLS server certificates issued on or after Sept. 1, 2020 must not have a validity period greater than 398 days.
This change will affect only TLS server certificates issued from the Root CAs preinstalled with iOS, iPadOS, macOS, watchOS, and tvOS. Additionally, this change will affect only TLS server certificates issued on or after September 1, 2020; any certificates issued prior to that date will not be affected by this change.

Connections to TLS servers violating these new requirements will fail.
This might cause network and app failures and prevent websites from loading.
(This change will not affect certificates issued from user-added or administrator-added Root CAs.)

"Apple has removed some apps from the App Store that install root certificates that could allow monitoring of data. If you have one of these apps installed on your device, delete both the app and its associated configuration profile to make sure that your data remains protected."

"Shortcuts let you quickly do everyday tasks, and with the apps you use the most
- all with just a tap or by asking Siri. Look for the Add to Siri button in your favorite apps
or visit the Gallery in the Shortcuts app to add new shortcuts.
Learn more in the Shortcuts User Guide."

"With iOS 12, iOS 13, and iPadOS, you can delete some built-in Apple apps
from your iPhone, iPad, iPod touch, or Apple Watch.

When you delete a built-in app from your device, you also delete any related user data & configuration files.
This can affect things like related system functions or information on your Apple Watch."

Starting in iOS 17 & iPadOS 17, Screen Distance is turned on by default for children under 13* in a Family Sharing group.
Viewing something like a device or book too closely for an extended period of time can increase eye strain and the risk of myopia. The Screen Distance feature in Screen Time uses the TrueDepth camera to detect when you hold your iPhone closer than 12 inches for an extended period, and encourages you to move it farther away. Screen Distance can help children engage in healthy viewing habits that can lower their risk of myopia and can give people of all ages the opportunity to reduce digital eyestrain. (If you don't want Screen Distance turned on, you can turn it off in iPhone or iPad settings.)
* Age varies by country or region.

"Aperture won't run in versions of macOS after macOS Mojave.
Here's how to move your Aperture libraries to Photos or Adobe Lightroom Classic..."
(See article for more details.)

"Update third-party video plug-ins to FxPlug4 to use them with Final Cut Pro on Mac computers with Apple silicon.

Click the links on this page to see which video plug-ins from these popular developers are compatible with Mac computers with Apple silicon. Check this page and the manufacturers' websites periodically for the most up-to-date information on FxPlug4 compatibility. "

"With macOS Catalina (and later), your iTunes media library is now available in the Apple Music app, Apple TV app, Apple Books app, and Apple Podcasts app. And Finder is where you can manage and sync content on your iPhone, iPad, and iPod touch..."

"In macOS Catalina or later, your previous iTunes media library is now available in the Apple Music app, Apple TV app, Apple Podcasts app, and Apple Books app. And when you back up your Mac, your media library is automatically included in that backup. When you set up a new Mac, you can also restore your Mac from a backup."

"If you can't change your payment method in the App Store or iTunes Store
On June 30, 2018, Apple will implement changes to continue to ensure your financial data is protected when you make purchases on the iTunes Store or App Store. As a result of the changes, you will no longer be able to change your Apple ID payment information from devices using the following versions of Apple software:

• iOS 4.3.5 or earlier
• macOS 10.8.5 or earlier
• Apple TV Software 6.2.1 or earlier*
  (* All Apple TV (2nd generation) devices are affected.)

If you're using one of these versions on your device and need to change your payment method, update your device to the latest version of the software... Or edit your payment information on a different device that uses more recent software."

"If you can't open the App Store or iTunes Store, buy content, or edit payment information
You might be using out-of-date software or hardware.
Some devices that use older software can no longer use the iTunes Store...
Some obsolete hardware products can no longer use the iTunes Store...
(see linked page above for more info.)

"If you have iOS or iPadOS 13, your iPhone or iPad storage is full, and the storage is mostly taken up by "Other" storage, update your device to iOS or iPadOS 13.6.1 or later.

Update your device
An issue in iOS or iPadOS 13 might prevent the system from freeing up storage for you.
To fix this issue, update your iPhone or iPad to iOS or iPadOS 13.6.1 or later.

If you don't have enough available storage to update wirelessly, update your device
to iOS or iPadOS 14.1 or later using a computer."

"When waking your Mac mini (Late 2012 or later) from Safe Sleep, you may notice that the sleep indicator light turns on and the system wakes but your display doesn't. This can occur if you have FileVault enabled.

To work around this issue, you can enter your password even while the display is dark. Then, press Enter. This should log you in and wake the display. "

"eGPUs are supported by any Mac with an Intel processor and Thunderbolt 3 ports, running macOS High Sierra 10.13.4 or later."
See Footnotes at bottom of linked page for info on specific configurations/issues.

"Depending on which Mac and macOS you're using, you might hear a startup sound
shortly after pressing the power button to turn on your Mac.

With macOS Big Sur 11 or later, you can control whether your Mac plays this sound at startup.
Choose Apple menu > System Preferences, then click Sound. In the Sound Effects pane,
use the "Play sound on startup" setting to turn the startup sound on or off."

"What to do if your computer restarts or shuts down unexpectedly, or you get a message that your computer restarted or shut down because of a problem."

"Your Mac periodically checks for unexpected firmware changes and allows you to transmit information about such changes to Apple.

If your Mac detects a difference between the firmware installed on your Mac and the firmware that its operating system (macOS) expects to see, it shows a message that "your computer has detected a potential problem." Firmware is software that allows your Mac hardware to work with macOS. Firmware that has been damaged or modified might affect the stability and security of your Mac.

To help Apple improve the stability and security of Mac computers, click Send to Apple to submit a report to Apple. You can also show the report to see the information that will be sent, or choose not to send it.

Then install the latest software updates, which can include firmware updates and other updates important to the stability and security of your Mac."

"Follow these steps if you can't install macOS Big Sur on a MacBook Pro (Retina, 13-inch, Late 2013) or MacBook Pro (Retina, 13-inch, Mid 2014).

When you install macOS Big Sur on these Mac models, the installer might say that the update cannot be installed on this computer, or your Mac might start up to a blank screen or circle with a line through it..."

"You just erased your Mac, and now the macOS installer can't find a user allowed to administer this computer.

When you erase the startup disk of your Mac, it's important to erase the volume group, which contains the system volume and data volume. If that wasn't done, the macOS installer might need to quit because it sees no users available for authorization. Follow these steps to resolve the issue..."

"The OS X Recovery Disk Assistant lets you create OS X Recovery on an external drive that has all of the same capabilities as the built-in OS X Recovery: reinstall Lion or Mountain Lion, repair the disk using Disk Utility, restore from a Time Machine backup, or browse the web with Safari.

Note: In order to create an external OS X Recovery using the OS X Recovery Assistant, the Mac must have an existing Recovery HD."

"Some system extensions aren't compatible with current versions of macOS or won't be compatible with a future version of macOS. Learn what to do if you see an alert about system extensions or kernel extensions..."

(Sometimes old Apple installers/updaters have expired certificates. An old tip was to set the system date back to allow them to be installed.)

"When you install macOS High Sierra on the built-in solid-state drive (SSD) of a Mac,
that drive is automatically converted to APFS.
Fusion Drives and hard disk drives (HDDs) aren't converted.
You can't opt out of the transition to APFS."

"Rosetta 2 enables a Mac with Apple silicon to use apps built for a Mac with an Intel processor.

Click Install, then enter your user name and password to allow installation to proceed. Rosetta will then be available for any of your apps that need it.

About Rosetta
Rosetta 2 works in the background whenever you use an app built only for Mac computers with an Intel processor. It automatically translates the app for use with Apple silicon.

In most cases, you won't notice any difference in the performance of an app that needs Rosetta. But you should contact the app developer to inquire about a version that can natively use the full power and performance of Apple silicon.

You can use Get Info to identify apps that need Rosetta or can use Rosetta:

1. Select the app in the Finder.
2. From the File menu in the menu bar, choose Get Info.
3. View the information labeled Kind:
   • Application (Intel) means the app supports only Intel processors and needs Rosetta to work on any Mac with Apple silicon.
   • Application (Universal) means the app supports both Apple silicon and Intel processors, and uses Apple silicon by default.

The Info window for universal apps includes the setting "Open using Rosetta." It enables email apps, web browsers, and other apps to use add-ons that haven't been updated to support Apple silicon. If an app doesn't recognize a plug-in, extension, or other add-on, quit the app, select this setting, and try again."

1. In the Finder, select the "Go" Menu.
2. Hold down Option key to make Library folder appear.
3. Go to Library/Printers and find your Printer's application.
4. "Get Info" on the printer application.
5. Check the "Open using Rosetta" option.

"If you're in Startup Manager and can't see a third-party startup disk, the startup disk could be using Option ROM firmware. To enhance system security, Mac computers with up-to-date software don't show devices that use Option ROM firmware until you load their firmware. To do that, press Option-Shift-Command-Period while in Startup Manager. If your startup disk appears, do that each time you want to start up from it or from another disk connected to it.

(If you're using a firmware password, the ability to load Option ROM firmware is disabled as an additional security protection.)"

"A very small number of customers with 2016 and 2017 MacBook Pro computers have experienced an issue with the battery not charging past 1%.
The battery health status on these devices will also indicate "Service Recommended." If the status indicates that your battery is Normal, your battery is not affected by this issue.

If your 2016 or 2017 MacBook Pro exhibits these behaviors, contact Apple to get your battery replaced, free of charge.
Your computer will be examined prior to service to verify that it is eligible for the free battery replacement.

Apple has also released a macOS update that prevents this issue from happening to other 2016 and 2017 MacBook Pro computers.
Please update to macOS Big Sur 11.2.1 or later or install the macOS Catalina 10.15.7 supplemental update."

"With iOS 13 and later, you can turn on Low Data Mode to restrict background network use
and save cellular and Wi-Fi usage.

You might want to use Low Data Mode if your cellular or internet plan limits your data usage,
or if you're in an area with slow data speeds..."

"You can't play sound in Dolby Atmos if Quick Start is turned off in Settings.
To check, go to Settings > Apps > iTunes Movies and TV Shows > Quick Start."

Info for Hardware and Software developers at developer.apple.com/homekit.

"Advanced Data Protection for iCloud offers Apple's highest level of cloud data security
and protects the majority of your iCloud data using end-to-end encryption."

• HEIF (High Efficiency Image File Format) for photos.
• HEVC (High Efficiency Video Coding), also known as H.265, for videos.

(FYI: An alternative to using Bootcamp (for those that don't need maximum performance) is running Windows (or other OS) on a Mac via a "Virtual Machine" using OS X compatible VM software like Parallels Desktop, Fusion or (freeware) VirtualBox. Check requirements for the VM -and- for the software/app you plan to use with the VM OS. The VM software vendor's user forums are also worth checking for info on compatibility/problems/performance. There are also some 'emulators' (i.e. Crossover, Wine) that may be useful, but generally have more limited compatibility compared to running the full OS.)

"What a revive does
In very rare circumstances, such as a power failure during a macOS upgrade, a Mac may become unresponsive and so the firmware on the Apple T2 Security Chip must be revived. A revive updates that firmware. A revive is designed to not make any changes to the startup volume, the user's data volume, or any other volumes.

Important: First try reviving the computer. If that fails or if you can't start the Mac from the startup volume, recoveryOS, or Internet Recovery, you must restore the firmware and erase the internal flash storage.

What does a revive do to your Mac?
A revive updates the firmware on the Apple T2 Security Chip. A revive is designed to not make any changes to the startup volume, the user's data volume, or any other volumes. User data may be retained if recoverable.

What does a restore do to your Mac?
A restore updates the firmware and erases recoveryOS and macOS on your internal storage. When this process is complete, any data on any internal volumes is unrecoverable.

You must restore the firmware and erase the internal flash storage if:
- Reviving the firmware was unsuccessful.
- You can't start the Mac from the startup volume, recoveryOS, or Internet Recovery.

(See linked article for more details and list of T2 chip Intel CPU Macs. Apple silicon Macs have no T2 Chip.)

• About the Firmware Restoration CD (Intel-based Macs) (now archived)
• Firmware Restoration CD 1.9 for Mid-2010 Mac Pro (MacPro 5,1)
• Firmware Restoration CD 1.8 for Early 2009 Mac Pro (MacPro 4,1) and Xserve 3,1
• Firmware Restoration CD 1.5 for Early 2008 Mac Pro (MacPro 3,1)
• Firmware Restoration CD 1.7 (see list of Mac models in article)
• Firmware Restoration CD 1.6 (see list of Mac models in article)
• Firmware Restoration CD 1.4 (see list of Mac models in article)

The Firmware Restore CD v1.4 doc links to an even older v1.3, but the link 404's. In case anyone really needs it, here's the (Archived) Software License Agreement for Firmware Restoration CD 1.3 that has a D/L link. (Update: D/L link now redirects to Apple Support home as of May 2017.)

Version 2.16 changes:
- Support for new hardware.
- Bug fixes and performance improvements.
(Requires macOS 12.4 or later.)

Version 2.15.1 changes:
- Support for new hardware.
- Bug fixes and performance improvements.
(Requires macOS 10.15.6 or later.)

Version 2.15 changes:
- Allow skipping the App Store pane in Setup Assistant.
- Support for restoring Mac computers with Apple silicon to macOS Monterey.
- Bug fixes and performance improvements.

Version 2.14 changes:
- New restrictions for Unpaired External Boot to Recovery and Unlock with Apple Watch.

Version 2.13.3 changes:
- Support for macOS Big Sur.
- Support for restoring macOS on Mac computers with Apple silicon.
- Web Clip: Configure Ignore Manifest Scope & Target Application Bundle Identifier.
- Bug fixes and performance improvements.
(Version 2.12.1 added support for restoring firmware on a 2019 Mac Pro & iOS VPN features.)

• iPad, iPad Pro, iPad mini
• iPhone
• iPod touch
• Apple TV (3rd generation) profile installation only
• Apple TV (HD or 4K)
• Apple silicon revive or restore on specific Mac computers.
  For a complete list, see Revive or restore a Mac with Apple silicon.
• Apple T2 Security Chip revive or restore on specific Mac computers.
  For a complete list, see Revive or restore Intel-based Mac firmware.