Switching DVD Region on iMac

Problem: An original set of DVD's do not play on my iMac. Some DVD's do play but do not know which region they are from?

Q: How do I change regions on my iMac for DVD's?

Since you are using VLC - per your other post - there is no reason to change the region as VLC does not recognize the region flag.

If you do get DVD Player reinstalled - need to realize you can only change the region setting 5 times and then it becomes permanent.

Best to keep using VLC if you're using multiple region discs.