Thought I might share this so others don't fall into the trap. Once you exceed your Cloudinary free account limits there is no going back. You receive a number of warnings and if you don't buy a paid account (min $10 a month) your account and all images will be deleted. I just migrated about 700 images back to my server and deleted my Cloudinary plugin.
Here's the reply from Cloudinary support:
"I apologize, regarding your question, once you exceed your plan limits, you receive a number of notifications about this, notifying you that you have exceeded your plan limits, requesting you upgrade your plan, as you have received. There is then a grace period during which you can upgrade and your account will remain fully functional. If these upgrade requests go un-answered and the issue is not taken care of, you are notified that your account will be cancelled and all images deleted be a certain due date. If still no action is taken and we are not contacted, the account is cancelled accordingly. We of course prefer to solve this before reaching this stage, by an upgrade or usage optimization."
use the function.
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