If you want to view public information without logging in, you can use a private browser window or log out of Facebook entirely. However, this won’t give you access to private profiles or stories. For stories, Facebook’s own feature notifies users when their story is viewed — there is no legitimate way around that.
I understand you're looking for information about an "anonymous Facebook viewer" — a tool or service that claims to let you view Facebook profiles, stories, or posts without the other person knowing. anonym facebook viewer
Here’s a clear, informative text on the topic: If you want to view public information without