How do I upgrade from macOS High Sierra to Catalina on a 2011 iMac?

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photosplorer Author

Level 1

4 points

How do I upgrade from macOS High Sierra to Catalina on a 2011 iMac?

how do upgrade my current OS , high sierra on a mid 2011 ,

21.5 inch , imac to say ... catalina ?

[Re-Titled by Moderator]

Original Title: OS upgrade

iMac 21.5″, macOS 10.13

Posted on Aug 27, 2026 4:39 AM

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Answer 1

Top-ranking reply

MartinR

Level 7

26,358 points

Aug 27, 2026 6:07 AM in response to photosplorer

You can't.

High Sierra (10.13.6) is the highest version of macOS that you can install & run on your 2011 iMac.

You would need at least a Late 2012 iMac 13,1 in order to install Catalina and even then you would be running an obsolete version of macOS on an 14-year old, obsolete computer.

You should consider replacing your 15 year old iMac. You have gotten lots of life out of it.

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Answer 2

MartinR

Level 7

26,358 points

Aug 27, 2026 6:15 AM in response to MartinR

Regarding your current 2011 iMac, your existing software will continue to run as long as the machine does.

Where you may already be encountering problems is online ... most browsers are no longer supported on High Sierra and the old versions that do run often don't work with modern websites due to changes in security controls. Firefox ESR is about the only browser still supported on High Sierra. But even Firefox support on High Sierra is scheduled to end in March 2027.

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