Error installing OSX on iMac (late 2012) after SSD upgrade

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srikfilms Author

Level 1

4 points

Error installing OSX on iMac (late 2012) after SSD upgrade

I mac late 2012 upgraded to ssd but error installing osx tried all possible ways

iMac 27″, macOS 10.15

Posted on Mar 11, 2026 1:35 AM

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Answer 1

Top-ranking reply

D.I. Johnson

Level 8

36,077 points

Mar 11, 2026 8:35 AM in response to srikfilms

Details matter, my friend.

• How, exactly, are you trying to install the OS? Bootable USB installer? Internet Recovery mode?

• Exactly what error are you getting?

• Did you erase and reformat this new SSD?

Use the GUID partition scheme and APFS format.

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

How to reinstall macOS - Apple Support

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Answer 2

VikingOSX

Level 10

124,652 points

Mar 12, 2026 5:08 AM in response to srikfilms

The latest operating system that you can install on that Late 2012 iMac is macOS Catalina (10.15.8). Of course, this could be folly on a 14-year-old Mac where anything electrical could abruptly end.

Booting should be from an external USB stick provided you have prepared the recipient drive properly (e.g. APFS for Catalina). You get the operating system from here, and then build the 16 GB USB stick from this article. Then, you boot with the option key to select the USB stick.

If that is not an internal Apple SSD, the installer may attempt to apply a firmware update to the drive, detect that it is not an Apple drive, and abort the installation.

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