For about eight hours on Tuesday morning, Apple asked visitors to checkcoverage.apple.com to enter their Apple ID for verification, where previously they just needed to enter a device's serial number ...
In an update to its warranty coverage utility, Apple now requires users to log in with the Apple ID associated with a device before being able to check its warranty ...
You can check if your device has a warranty via Apple's warranty tracker or the Settings app. You'll need to enter your serial number to get full information on your warranty and other coverage.