https://www.theverge.com/2017/9/4/16251200/apple-leaked-iphone-warranty-guide-repair-replace

A new leaked warranty guide for Apple iPhones shows how the company determines which iPhones are eligible for repair under warranty. Conditions are outlined for in-warranty repair, out-of-warranty repair, and devices categorized as “ineligible” due to damage or unauthorized modification. The 22-page guide is dated March 3, 2017 and was leaked recently to Dropbox, reports Business Insider. Called the “Visual/Mechanical Inspection Guide” (VMI) the document covers the iPhone 6, 6 Plus, 6S, 6S Plus, 7, and 7 Plus.

The types of damage that Apple covers under its warranty service includes debris under display glass or pixel anomaly, a misalignment of the FaceTime camera foam, or a single hairline crack to the front glass without an impact point. The VMI notes that devices with these types of impairments are covered regardless of any accidental or liquid damage.