Turn this on for daily or recurring monitoring of the same destination search or hotel/search URLs. The first run returns all matching hotels as NEW. Later runs normally return only NEW, UPDATED, and REAPPEARED hotels. Turn on "Emit unchanged" or "Emit expired" only when you also want those hotels returned (and billed). Hotels are compared on their listing content (name, ratings, review count, price and totals, rooms, amenities, policies, address, deals); the photo set (extra.images, extra.gallery) is never compared because the site rotates it, and by default these are also left out of change detection but still returned: extra.checkIn and extra.checkOut (they roll forward daily when Check-in/Check-out are left empty), availability scarcity messages, sponsored flag, search rank, price messages, map image and search URL. Add more in Ignore fields when detecting changes below. State is kept separately for each mode/destination/URL/filter setup; use State key when you want to name or deliberately share a monitoring campaign. To continue one specific interrupted run instead, use Resume from a previous run above.