This is a mirror of the tip on Apple support communities, with updates from the author on the author's website: http://www.macmaps.com/*
This tip is from a series of tips of upgrading Mac OS X 10.7 Lion, 10.8 Mountain Lion, 10.9 Mavericks, 10.10 Yosemite,10.11 El Capitan, 10.12 Sierra ,10.13 High Sierra, 10.14 Mojave, 10.15 Catalina client editions. Server edition forum is over here:
https://discussions.apple.com/community/servers_enterprise_software/macos_server
Note: some people have had trouble downloading the latest Catalina links. https://brave.com/ has been found to be a better web browser than some if you run into issues.
Here is the client forum:
https://discussions.apple.com/community/mac_os/catalina
On October 7, 2019, Apple released Mac OS 10.15.
July 15, 2020 Apple released 10.15.6 Combo, and Delta.
June 15, 2020 Apple released a 5600M Radeon patch for MacBook Pros with the graphics chip (see your System Profiler to determine which graphics chip you have and if it matches the one the patch addresses). This may be the same issue that has affected certain Macs from 10.15.1 on with a blank screen after upgrading past 10.15.2. The 5500M which has been reported as having similar issues is NOT documented as being addressed by this patch.
Before installing anything new, a backup is essential http://www.macmaps.com/docs/DOC-1992
This is especially important, as there is a bug that may cause data loss when using Mac OS Mail application within Catalina. Currently that bug's status is unknown, but has been reported on several Mac news websites. One news website actually suggested using a system optimizer that mentioned the bug. However, optimizers should never be used on Macs as they can cause data loss in of themselves.
Make sure everything you have from software to hardware is compatible with Catalina before upgrading, or needs it.
These Macs are compatible with 10.15 (with their Model Identifier/ Machine ID from the system profiler in x,x format). No Snow Leopard 10.6 compatible Mac can be upgraded to Catalina. As a result there is no PowerPC application support on a separate boot for Macs compatible with Catalina.
MacBook early 2015 8,1 (shipped with 10.10.2)
iMac Late 2012 12,1 (Shipped with 10.8.2)
MacBook Pro Mid-2012 9,1 (shipped with 10.7.3)
Mac Mini Late 2012 6,1 (shipped with 10.8.1)
MacBook Air Mid 2012 5,1 (shipped with 10.7.4)
Mac Pro 2013 9,1 (shipped with 10.9.1)
No 32 bit application or driver is compatible with Catalina. If you find after the fact your applications are not compatible, you can partition a hard drive to install an older OS (note the third option for booting to install older systems), if your Mac is older than Catalina's release date.
http://www.roaringapps.com/ is starting to list compatible software for Catalina. Do not use reports that predate October 7, 2019. Further information on its compatibility with applications can be determined through the System Report (a.k.a. System Profiler) information from Apple menu (the menu in the upper left corner with the Apple logo)-> About This Mac. Only those applications that say "Yes" under 64-bit (Intel) are compatible. You can even click on the column header to sort 64-bit (Intel) to group just the applications you need to update for Catalina. Notice how in the image below the arrow on the far right with the 64-bit (Intel) is pointed up. This brings the non-64-bit applications up first.
If About This Mac is slow, you can use
https://www.stclairsoft.com/Go64/index.html
To determine what software is native.
The following peripherals have Catalina pages of info from their manufacturers on Mac compatibility:
Ricoh: On October 24th 2019, Ricoh updated many of their Sierra and later drivers including drivers compatible with Catalina on the website. Select the Or Option on the right side of the page to find out if yours is one of them.
Epson has this help page for scanners. Their printer support is on the driver individual pages.
https://epson.com/s0/macOS-10-15-Catalina-Support/s/SPT_CATALINA-NS
has more tips from Epson.
More info will be added as it becomes available.
The direct download link for Catalina is here:
https://apps.apple.com/us/app/macos-catalina/id1466841314?ls=1&mt=12
If the installer fails, ask a question in the forum, and gather the results from Etrecheck to help us identify your issues:
https://discussions.apple.com/docs/DOC-250002463
A method of installing Catalina in unsupported mode on older Macs is available here:
You are on your own if you attempt to try this.
For those interested about news about the upcoming Big Sur operating system that is spreading on the net, give Apple a chance to to bring a forum on this board to discuss it. Until then much is speculation, except what http://www.apple.com/pr
has to say about it. Compatibility tables including Mac OS 11.0, or 10.16 should be treated with a grain of salt until the operating system is officially released and out of beta. If you are a beta tester, please use the lines of communication on Apple's Developer website.
* Links to my page may give me compensation.