CHECK THE WARRANTY FROM THE SETTINGS
The Settings app is the best place to start if you’re using a current version of iOS to determine whether your iPhone is still under warranty. Just find the Settings app on your iPhone and launch it. Next, go to the About page that you may find under General.
USE THE APPLE SUPPORT APP
USE APPLE’S CHECK COVERAGE WEBSITE
Using Apple’s official check coverage website is another option to determine whether your iPhone is still covered by its warranty. All you have to do is locate the alpha-numeric serial number of your iPhone and enter it into Apple’s Verify Coverage page.
USING APPLE MY SUPPORT WEBSITE

Apple provides a web version of the My Support App that can be viewed from any device with a web browser in addition to the My Support App that can be downloaded to your iPhone. When you arrive at the My Support website, you may sign in using your Apple ID to access a wealth of information on your Apple products.
