Do western digital hard drives support iMacs?

I have one that I use for Time Machine. it works great.

AFAIK, you will only run into compatibility issues if you use WD's bundled software that supposedly makes the drive "Mac ready". it is always best to erase and format a drive before putting it into service.

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

In general, yes, they do. But don’t trust any article that you happen to find somewhere in a magazine or on the Internet. Go to the Western Digital website and look up the specs for the drive.

Also, the advice that jeffreythefrog already gave you is good advice.