The review lives in Settings → Privacy & Security → Photos: a list of every app that has requested photo access, with its current level. (Per app: Settings → Apps → [app] → Photos.)
The levels: None; Add Photos Only (the app can save into your library but can't read it); Limited Access (you selected specific photos or albums; the app can ask to add more); Full Access (the entire library, including metadata like locations and captions — iOS shows you the photo/video count before granting).
What to look for: Full Access on apps that don't need it (a QR scanner shouldn't see your whole library), and old apps you no longer use. Revoking or downgrading is instant; apps handle 'no access' by showing an empty picker.
Practical recommendation: Full Access only for your actual photo apps and editors you trust; Limited Access for everything that just needs to attach a photo occasionally; Add Photos Only where saving is the only need. The App Privacy Report (Settings → Privacy & Security → App Privacy Report) then lets you verify how often apps really touch your library over the following 7 days.
— Osnivo Guides