You may see variations like "Instagram private story viewer." These are equally fraudulent. Instagram Stories are ephemeral, but they follow the same server rules: only approved followers can view them.
You may be asked to complete a “human verification” step—like a survey, downloading another app, or entering your phone number. This generates affiliate revenue for the scammer. You’ll never see the private content, but you may face unwanted subscriptions or spam calls. Instagram-private-photo-viewer
Some older viewer tools claimed to exploit a feature called "zombie followers"—users who unfollowed you but still saw your stories due to a cache glitch. This bug was patched by Instagram in 2019. As of today, there is no known, active exploit that allows a third-party tool to view private photos. You may see variations like "Instagram private story viewer