Iphone XR heating while charging.

If it is getting heated up check the cable.

Identify counterfeit or uncertified Lightning connector accessories

Apple recommends using only accessories that Apple has certified and that come with the "Made for Apple" badge. Learn about the issues that counterfeit or uncertified Lightning accessories can cause and how to identify these accessories.

If you use a counterfeit or uncertified Lightning accessory, you could see these issues:

• Your iOS device could become damaged
• The cable might be easily damaged
• The connector end might fall off, get very hot, or might not fit properly into your device
• You might not be able to sync or charge your device

Only Apple makes the USB-C to Lightning Cable. There are no "Made for Apple" USB-C to Lightning cables.

Compare packaging and writing on the cable

To identify counterfeit or uncertified cables and accessories, look carefully at the accessory's packaging and at the accessory itself. Certified third-party accessories have the MFi badge on their packaging:

Some accessories might have a previous version of the MFi badge:

An Apple Lightning to USB cable has "Designed by Apple in California" and either "Assembled in China," "Assembled in Vietnam," or "Indústria Brasileira" on the cable about seven inches from the USB connector. You'll see a 12-digit serial number at the end of this text.

A certified, third-party Lightning to USB cable usually has company branding on the Lightning-connector end.

Identify counterfeit or uncertified Lightning connector accessories ...

https://support.apple.com/en-us/HT204566

Fast charge your iPhone

Use fast charge with iPhone 8 or later. You can recharge your iPhone up to 50 percent battery in 30 minutes.*

Fast charging gives you a quick and convenient way to recharge your iPhone 8 or later. Your iPhone fast charges up to 50 percent in 30 minutes when you use an Apple USB-C to Lightning cable and one of these adapters:

• Apple 18W, 29W, 30W, 61W, or 87W USB-C Power Adapter
• A comparable third-party USB-C power adapter that supports USB Power Delivery (USB-PD)

If you're not sure which Apple Power Adapter you have, check the wattage on the bottom of the adapter:

If nothing works take your device to an Apple Retail Store or Apple Authorized Service Provider, or contact Apple Support:

Apple Repair and Repair Status Check - Official Apple Support

https://support.apple.com/repair

Apple Authorized Service Provider

https://locate.apple.com › Home › Find Locations

Find Locations - Location Selector - Apple

https://locate.apple.com › Find Locations

Contact Apple for support and service - Apple Support

https://support.apple.com/en-us/HT201232

As long as the device was sold in the Apple Store, I would imagine that it is MFi certified. It would say so on the box. A larger capacity power converter like that will charge the iPhone faster, and in doing so with make the back of the iPhone feel warm. It is the chemical reaction in the battery while charging that causes that. Warm is not a problem, but if it gets too hot to hold, that could indicate a problem.

Okay, like I said in my first response, warm is expected, but hot indicates a problem. Of course how hot it gets can be subjective, but if you are concerned, then make a Genius Bar appointment at the nearest Apple Store and have it examined by Apple. The iPhone XR would still be under warranty.