All iPhones pick up fingerprints, and it’s all too easy to get your iPhone dirty with ink, lotion, makeup, dirt, food, and oil. If you’re faced with an iPhone that needs cleaning, resist the urge to spray it with window cleaner, rubbing alcohol, or ammonia, or, even worse, to scrub it with baking soda or Borax. That’s because all iPhones have oleophobic—oil repellent—coatings on their glass surfaces that make it easy to wipe off fingerprints. You don’t want to remove that coating any faster than it will wear off normally, and cleaning products will strip it quickly. Instead, Apple recommends a soft, lint-free cloth such as you would use for glasses or camera lenses.
By the way, even though the iPhone 7 and later have some level of dust and water resistance, it’s important to avoid getting moisture in the openings—most of the time, a lens cloth should be all you need.