Can I uninstall Catalina and go back to Mojave? My mac mini is so slow now.

designer_1983 wrote:

How can I check what is slowing my mac mini down before reverting ?

To trouble shoot further you can:

—Try a SafeBoot https://support.apple.com/en-us/HT201262

Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc. Login and test. Reboot as normal and test as caches get rebuilt.

In Safe mode third party system modifications and system accelerations are disabled, it removes malware, etc hampering smooth operation, however a reboot will put it back to normal mode.

This test will tell you if third party interference; extensions etc are not loaded in safe boot mode.

—Test issue in another user (or guest user) account  https://support.apple.com/en-us/HT204443

This will tell you if it a universal issue or isolated to your user/admin account. 

Always advised to Uninstall all third party apps that are Cleaners/Optimizers/Anti-Virus

designer_1983 wrote:

Can I uninstall Catalina and go back to Mojave? My mac mini is so slow now.

Revert to previous macOS

https://support.apple.com/en-za/guide/mac-help/mh15216/10.15/mac/10.15

Yes. Just use your backup.

WD

You should go up and not back.

Big Sur works just fine.