OS 10.11 DOWNLOAD
How to download OS 10.11 on a 2009 Mac
iMac, OS X 10.11
Question marked as
Top-ranking reply
The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.
With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install. For Best results use Safari to commence the download as Others may not work.
Safari will open a redirect and open the Apple Store where the download can commence
https://support.apple.com/kb/SP728?locale=en_CA
Make Time Machine Backup is very useful and can be used to Revert to Previous Working macOS
Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation
