changing the privacy of a post on facebook?

[K]

If someone likes your post and you change the privacy if the post they liked will they know that I changed the privacy?

[WebCompTech]

No, they won't know you've changed the privacy options on the post. No notification is sent to them. Also, if they are no longer able to see the post, their "Like" will be removed and not shown on the post either. It will, of course, become obvious to them they have been removed if they go back to your Facebook page to look at the post or picture again, but can no longer see it.