Downgrade to an older version of OS X
Installing an older version of OS X isn’t as easy as you think it would be, writes Glenn Fleishman
Macworld reader Roxsanne Roush wants to go back in time. She purchased a 2011 iMac that had El Capitan installed, but needs to run a previous version of OS X as she relies on Adobe Creative Suite 5.5. She wants to revert to Mavericks.
It always makes me nervous moving backwards with operating systems, because so much can go wrong. The easiest way to revert is to install an older, compatible version of OS X on an external drive. The 2011 iMac models have USB 2.0 but also FireWire 800. You can purchase a FireWire 800 drive that’s probably faster than the internal drive and offers more capacity at a reasonable price. Download the Mavericks installer – obtaining it can be a challenge if you don’t have a copy already – and choose the external drive as a target. Then you can use the Startup Disk preference pane to switch drives if you want to swap between using Mavericks and El Capitan.
Since you don’t have much on the iMac, you could copy the files you need, and perform and erase and install operation by creating a bootable flash drive version of the Mavericks installer.