In the majority of social media apps that have story features, such as Snapchat, Instagram, and Facebook, the person who posts the story cannot tell if you replay it. These platforms are designed to respect the privacy of the viewer in this regard. Replaying a story is seen as an individual action that doesn't require the knowledge of the story creator. This allows users to freely go back and review a story if they want to without the worry of the creator being notified.
Yes, usually people can see if you replay their story. Most social media platforms have features that notify the original poster when their story is replayed.
Well, on Snapchat, the functionality is such that when it comes to Snap Stories, the person who posted it won't get any notification if you replay it. It's different from normal snaps in your chat, where replay might be restricted or the sender could be notified in some cases. But for Snap Stories, it's a more public - viewing kind of thing and there's no such 'replay detection' for the story creator.
On some social media platforms, you can see the number of replays for your story. For example, Instagram provides insights that may include information about how many times your story has been replayed. However, not all platforms offer this feature. Some may only show views or other engagement metrics like likes and comments, but not specifically replays.