I took my Mac into my local Apple Store and they said they hadn't heard of something like this before. Unfortunately, they recommended wiping the Mac and reinstalling Mojave as a clean install. They said there might be a problem with Catalina if that's what caused the problem so to wait until the next incremental release before updating. Another of the main reasons as to why your Catalina Slow could be that you have an abundance of junk files from your system in your current OS before updating to macOS 10.15 Catalina. This will have a domino effect and will start to slow your Mac down after you have updated your Mac. The most recent version of Apple’s MacOS — known as Catalina — is having a major impact on those that upgraded without understanding that their older 32-bit programs would no longer run. In my example, I had macOS Catalina 10.15.7 Supplemental Update waiting, and the notes below clearly say that this update “improves the security of macOS.” There was also a Safari update to 14.0.1 which had some speed enhancements but also security fixes, including the removal of support for Adobe Flash. I only recently upgraded my 2012 Mac Mini to Catalina as took me a while to phase myself out of two 32bit apps. No real issues with the upgrade. However the one thing I hadn't realised is the rebranding of the iTunes app to 'Music', Apple also removed all the preloaded Internet Radio stations to encourage uptake of their paid Apple Music.

1. My Macbook Pro Will Not Update To Catalina
2. Why Is My Mac Not Updating To Catalina 10.15.6
3. My Mac Is Not Updating To Catalina

This page covers 5 fixes for Mac won't boot or start issue after macOS Big Sur, Catalina, Sierra or older macOS update issue. If you are with this issue, follow to make your Mac computer work now:

macOS has now been updated to 11.0, and many Mac users are trying to upgrade to the newest version. While for most it's a usual pleasurable experience, for some this update had downsides. Some users complain that their Mac computers won't boot after installing new macOS Big Sur/Catalina. When Mac fails, it usually can't boot or start up properly. If you are faced with this situation, the most important thing should be recovering data from the unbootable Mac because:

• Your attempts to fix the Mac not booting issue may write new data on this Mac, which will overwrite the old data and make it irrecoverable.
• Recovering data before the complex fixes can avoid data loss.

EaseUS Mac data recovery software is able to recover data from unbootable Macs after update. It creates a bootable media that enables you to recover data from Mac hard drive (If you only have one Mac). What's more, it recovers data from failed internal Mac hard drive, APFS boot drive, and unmountable APFS boot volume, etc. If you have two Mac devices, take out the hard drive and connect it to the other Mac. Download EaseUS Data Recovery Wizard for Mac on that Mac device, and recover data from the hard drive.

Then, you can read on and Fix the 'Mac won't boot after update' issue after you have successfully got data from the drive.

1. Reset the PRAM / NVRAM

NVRAM refers to special memory sections on your Mac that store data that persists even when the Mac is shut off, such as volume settings and screen resolution. Resetting that data isn't harmful! In some cases, after performing this step, your Mac will restart normally.

• Restart your Mac
• Hold down all of these keys: 'Command', 'Option', 'P' and 'R', and turn on the Mac. (It's the same keys to reset the PRAM).
• Keep holding the keys down until you hear the Mac restart again.

You may see a progress bar on startup. If the progress bar fills up and then the Mac starts up, you're probably good to go. If not, reset SMC.

2. Reset the SMC

In some situations, you may need to reset your Mac's SMC (System Management Controller).

• Shut the Mac down.
• Unplug all cables.
• Wait for a few minutes.
• Plug the cables back in and start up the Mac.

If you've got a Mac desktop, unplug it for 15 seconds and then plug it in and after five seconds press the power button.

3. Boot Mac in Safe Mode

Safe Mode is a stripped-down version of the Mac operating system that can be useful if you are trying to troubleshoot issues with your Mac.

• Start your Mac, press and hold the 'Shift' key, and make sure your Mac has at least 9 GB of free space.
• When the login window appears to release the shift key and log in. You may be required to log in twice if you have FileVault turned on. Then restart the device.

Wait patiently till Mac computer finish the reboot process.

4. Run Disk Utility in Recovery Mode

If your Mac is booting but the operating system isn't loading up, you may have a corrupted drive. Luckily it is possible to fix this in Recovery Mode. In Recovery Mode you can restore from a Time Machine backup, use Disk Utility to verify and repair connected drives, check your internet connection, get help online using Safari, and install or reinstall macOS.

• Make sure the Mac is off. If it's stuck on a grey, blue or white screen, just hold down Mac's power button for several seconds until it shuts off.
• Hold down the 'Command' and 'R' keys, and power the Mac back up again. Keep pressing 'Cmd' + 'R' while your Mac is booting up.
• Once your Mac starts in Recovery Mode you can have access to 'Utilities'. Click 'Disk Utility', locate the icon for your Mac's drive, and click 'Verify Disk'.

5. Reinstall macOS Big Sur/Catalina/Sierra

The last method to fix macOS Big Sur, Catalina or Sierra fails to boot after update error is to reinstall macOS.

• You can download wanted macOS Big Sur/Catalina/Sierra and create a bootable USB drive to clean install macOS Big Sur/Catalina/Sierra on your computer again.
• You can also boot into Recovery mode (Solution 4), and then click to install the latest OS and follow the onscreen prompts. Our article on resetting a Mac to factory settings has more information on reinstalling macOS.

If your Mac does not respond after trying these tips, contact Apple Support or a certified Apple Repair Center. It’s likely there is a problem with your logic board or other internal hardware.

If you haven't updated to Catalina yet, read on to find out how to update to Catalina or Mojave from High Sierra, Sierra, El Capitan, Yosemite, or even older version of Mac OS X below.

Which Mac operating system is the best is a topic of numerous debates among Apple fans.

Since the mission of this blog is to refute myths and legends around Macs, it’s time for me to provide my 2 cents about the issue on hand. While everything below is just my opinion, as a long-time Mac user and veteran software engineer, I hope my opinion worth something.

The best Mac OS version is the one that your Mac is eligible to upgrade to. In 2021 it is macOS Big Sur. However, for users that need to run 32-bit apps on Mac, the best macOS is Mojave. Also, older Macs would benefit if upgraded at least to macOS Sierra for which Apple still releases security patches.

1. In the case of Catalina that includes all the old-style Mac Pro models, pre-'trash can'. If you want to run, but your Mac is older than 2013/2014, the new macOS just isn't for you, as far as.
2. NOTE: If your Mac came with macOS Catalina, you can restart your Mac while holding down Shift-Option-Command-R to enter Internet Recovery Mode and install the operating system that came with your Mac. Otherwise, follow the steps below to install Catalina back on your Mac. Connect your Mac to the internet via Wi-Fi or Ethernet.

How to Tell Which macOS You Are Running

To find out which macOS is currently running on your Mac, follow these steps:

1. Click on Apple logo in the top left corner of the menubar
2. In the dropdown click on the first item: About This Mac
3. The first line in the Overview tab is the name of the current OS.

What Version of OS Can My Mac Run?

Not all Macs can be upgraded to the latest OS version. For instance, old Macs powered by PowerPC CPUs cannot run OS intended for Intel-based computers. Also, some versions have hardware limitations.

For instance, Mojave cannot be installed on MacBook Pro earlier than Mid 2012 model.

Check below to know exactly what version of OS your Mac can run.

Which OS is Best for my Mac

Anytime someone asks me which OS is best for them I always suggested going with the latest. Things have changed recently, however.

Should I Upgrade to macOS Catalina or Big Sur?

While personally I like macOS Big Sur and have it installed on my MacBook Pro, it comes with serious breaking changes.

The first issue is compatibility.

Big Sur is a transition OS which is designed to help Apple to move from Intel processors to their own chips on ARM.

After I installed Big Sur on my MacBook Pro mid 2020 (pre-Silicon), most of my apps, including Microsoft Office, were working as expected.

However, my VMWare Fusion 11 does not start anymore, so I have to purchase a new license if I want to keep using it (or roll back to Catalina). Luckily, I took a full backup before the upgrade.

The second breaking issue is the lack of 32-bit app support.

macOS Catalina and Big Sur can only run 64-bit apps.

If you wondering whether you should upgrade to macOS Catalina or Big Sur, first verify that you don’t have any 32-bit apps. But first, take a back up, so you can go back in case something breaks after the upgrade.

For instance, I had to remove uTorrent after upgrade. And I didn’t know that uTorrent is 32-bit!

How to Know If App is 32-bit or 64-bit

To find out whether the app on your Mac is 32-bit or 64-bit follow these steps:

1. Click on Apple logo in the top left corner of the Mac screen
2. Click on About This Mac option
3. Click on System Report button in Overview tab (first one)
4. Scroll down to Software -> Applications
5. Find the app and check Kind

Which macOS Should I Use

If you have an older Mac which is not eligible to upgrade with some latest software or hardware, I’d suggest upgrading at least to Sierra (or better High Sierra) for the following reasons:

• Sierra is still supported by Apple, and it gets security updates
• APFS file system is available
• It supports Siri
• Significant security improvements

The most important point when choosing the best OS is the ability to get security updates. While Apple generally does not announce the OS end of life dates, it is possible to know when they stop releasing security updates from this page.

For instance, according to the page, the last security update for OS X Yosemite was released on September 12, 2017. The last update for OS X El Capitan was in July 2018, and Carnegie Mellon University confirmed that El Capitan’s end of life date was August 2018.

Snow Leopard Myth

I know that some users on forums believe that the best OS version for Macs was Snow Leopard. But that is a myth. And I know how such myths get created.

Once I worked in the company, which was selling a 20-year old product. And customers were still using and didn’t want to switch to new versions, because the old one was rock solid.

I then talked to the engineer who worked on the project, and he revealed that the product was a total disaster when it was first deployed. Engineers had to work on-site for almost a year in order to fix all bugs.

After five or so years of polishing the product, it becomes virtually bug-free, and nobody now remembers how bad it was when it was first rolled out. A similar thing happened Snow Leopard, and it was recognized as best mac os version after some time.

How to Update to the Latest Version

There are two ways to update to the latest OS version on Mac:

• From the Software Update section in System Preferences
• Use a download link

Using Software Update

This is by far the best option, but it only available if you have Yosemite, or later OS installed already. If you enabled automatic updates, then Mac will inform you that the next macOS is available.

Just open System Preferences, go to Software Update and click on the Upgrade Now button.

This method is also best if wondering how to check if you have the latest version of OS installed on your Mac. Only the version compatible with your hardware will appear here.

For instance, my the latest version for Mac Mini 2012 is Mojave, I can’t install anything newer than that.

Using download links

For older systems or in case you need to downgrade, you have to download a standalone installer in DMG format. DMG stands for disk image, similar to ISO, just different formats.

After downloading the installer, just double click on it and follow instructions. Again, do not forget to take a backup before the upgrade.

Mac OS Comparisons: Requirements, Features, Compatibility, Download Links

Following is a high-level description of all Mac operating systems as early as Mountain Lion.

You can refer to those descriptions when deciding which operating system is best for your iMac, Mac Pro, Mac mini, or MacBook.

With each OS description, I included a list of Macs supported. However, you can use Mac OS compatibility checker for more detailed information.

macOS 11 Big Sur

macOS v11 (codename Big Sur) is the latest version of the operating system for Apple computers.

Release date: October 13, 2020

Hardware Requirements: RAM requirement 4GB. Big Sur is the first OS to support new Macs using ARM technology (in the future).

Features

• The biggest design refresh since macOS X.
• Support for new ARM processors.
• Safar improved performance and power consumption.
• Time Machine supports backup to APFS volumes.
• One-click translation for 7 languages.
• Redesigned maps

Software Compatibility Issues

Only 64-bit apps are allowed to run on Big Sur.

How to install

There are two ways to install Big Sur: enable automatic updates in System Preferences or download by using the following link.

List of Apple computers compatible with macOS Big Sur

• MacBook (2015 and later)
• MacBook Air (2013 and later)
• MacBook Pro (2013 and later)
• Mac mini (2014 and later)
• iMac models (2014 and later)
• iMac Pro (2017 and later)
• Mac Pro (2013 and later)

macOS 10.15 Catalina

Release date: October 7, 2019

Hardware Requirements: RAM requirement increased from 2GB to 4GB.

Features

• Introduced Sidecar, which allows for Macs to use an iPad as an external display.
• iTunes was replaced by separate apps: Music, Podcasts, and TV.
• Find My Mac and Find My Friends have merged into one app.

Software Compatibility Issues

macOS Catalina is the first Mac operating system that does not support 32-bit applications. Only 64-bit apps are allowed to run on Catalina.

How to install

There are two ways to install Catalina: enable automatic updates in System Preferences or download by using the following link.

List of Apple computers compatible with macOS Catalina

• MacBook (Early 2015 or later)
• MacBook Air (Mid 2012 or later)
• MacBook Pro (Mid 2012 or later)
• Mac mini (Late 2012 or later)
• iMac models (Late 2012 or later)
• iMac Pro (All models)
• Mac Pro (Late 2013)

macOS 10.14 Mojave

Release date: September 24, 2018

Hardware Requirements: 2GB RAM and 18.5GB free space on disk

Features

• The main feature of Mojave is “Dark Mode”
• FaceTime adds group feature which allows chatting with up to 32 people
• News, Stocks, Voice Memos, and Home apps were ported from iOS to Mac.

How to install

If your Mac is eligible to update to Mojave, then the easiest way to install it is by enabling automatic updates. Downloading a standalone Mojave installer could be a little tricky.

List of Apple computers compatible with macOS Mojave

• MacBook (Early 2015 or later)
• MacBook Air (Mid 2012 or later)
• MacBook Pro (Mid 2012 or later)
• Mac mini (Late 2012 or later)
• iMac (Late 2012 or later)
• iMac Pro (All models)
• Mac Pro (Late 2013 and 2010-2012 models with upgraded GPU)

macOS 10.13 High Sierra

Release date: September 25, 2017

Hardware Requirements: 2GB RAM and 14.3GB free space on disk

Features

• APFS (Apple File System) becomes the default file system in High Sierra. It’s a significant upgrade from the older HFS+ in terms of speed, size, and security
• iCloud support of Messages which allows sync messages of the account across multiple devices
• Mail app uses 35% less storage space due to optimizations

List of Apple computers compatible with macOS High Sierra

• MacBook (Late 2009 or newer)
• MacBook Pro (Mid 2010 or newer)
• MacBook Air (Late 2010 or newer)
• Mac mini (Mid 2010 or newer)
• iMac (Late 2009 or newer)
• Mac Pro (Mid 2010 or newer)

How to install

Here is a High Sierra download link.

macOS 10.12 Sierra

This is the first macOS version. Previous OS versions for Macs were called OS X (X stands for 10).

Release date: September 20, 2016

Hardware Requirements: 2GB RAM and 8GB free space on disk

Features

• Siri was introduced to Macs
• Optimized storage with iCloud sync
• Auto-lock feature allows unlocking MacBook with paired Apple Watch
• APFS preview available
• Disk Utility can manage RAID sets again
• Significant security improvements

How to install

Here is a Sierra download link.

List of Apple computers compatible with macOS Sierra

• MacBook (Late 2009 or newer)
• MacBook Pro (Mid 2010 or newer)
• MacBook Air (Late 2010 or newer)
• Mac mini (Mid 2010 or newer)
• iMac (Late 2009 or newer)
• Mac Pro (Mid 2010 or newer)

OS X 10.11 El Capitan

How To Update Old Macos To Catalina

Last OS X version.

Release date: September 30, 2015

Hardware Requirements: 2GB RAM and 8GB free space on disk

Features

• System Integrity Protection – a security feature that protects even when the root user executes the process
• Performance improvements: open PDF files four times faster, Mail is twice faster, launching apps 40% faster
• Notes app similar to the app in iOS

Macs compatible with OS X El Capitan

same as OS Mountain Lion.

How to install

Here is El Capitan download link.

OS X 10.10 Yosemite

Release date: October 16, 2014

Hardware Requirements: 2GB RAM and 8GB free space on disk

Macs compatible with OS X Yosemite

Same as OS Mountain Lion.

Features

• Major user design overhaul
• Introduction of Handoff and Continuity features
• Photos app replaced iPhoto and Aperture

How to install

Here is Yosemite download link.

Should I Upgrade Old Mac To Catalina

OS X 10.9 Mavericks

First free Mac OS. Previous OS versions vary from $19.99 to $129.

Release date: October 22, 2013

Hardware Requirements: 2GB RAM and 8GB free space on disk

Features

• Compressed Memory feature automatically compresses inactive apps when approaching maximum memory capacity
• Timer coalescing is a feature that reduces CPU usage by up to 72 percent
• App Nap puts apps that are not currently visible to sleep

Macs compatible with OS X Mavericks

Same as OS Mountain Lion.

Update Old Macbook Air To Catalina

How to install

OS X Mavericks installer is not available on Apple Site. Follow instructions here to install Mavericks.

OS X 10.8 Mountain Lion

Must be purchased. Fixed many bugs introduced in OS X Lion.

Release date: July 25, 2012

System Requirements: 2GB RAM and 8GB free space on disk

Features

• New apps: Notification Center, Notes, Messages, Game Center
• AirPlay mirroring allowed to mirror Mac screen to Apple TV
• Application updates automatically install from the App Store

My Macbook Pro Will Not Update To Catalina

List of Apple computers compatible with OS X Mountain Lion

• iMac (Mid-2007 or newer)
• MacBook (Late 2008 Aluminum, or Early 2009 or newer)
• MacBook Air (Late 2008 or newer)
• MacBook Pro (Mid/Late 2007 or newer)
• Mac mini (Early 2009 or newer)
• Mac Pro (Early 2008 or newer)
• Xserve (Early 2009)

How to install

Mountain Lion installer is not available on Apple Site. Follow instructions here to install OS X Mountain Lion.

List of older Mac OS Versions

Following Mac OS versions are still running on older Macs, but Apple does not support them anymore, and there is no point to upgrade (or downgrade) to them:

Why Is My Mac Not Updating To Catalina 10.15.6

• OS X 10.7 Lion
• OS X 10.6 Snow Leopard
• Mac OS X 10.5 Leopard
• Mac OS X 10.4 Tiger
• Mac OS X 10.3 Panther
• Mac OS X 10.2 Jaguar
• Mac OS X 10.1 Puma
• Mac OS X 10.0 Cheetah

My Mac Is Not Updating To Catalina