Can I use my iPhone 8 charger with my iPhone 23 ProMax?
Will using my iPhone 8 charger harm the battery or functionality of my iPhone 13 Pro?
iPhone 13 Pro Max
Question marked as
It won't harm it. Apple encourages using it. See the following from https://www.apple.com/shop/buy-iphone/iphone-13-pro
As part of our efforts to reach our environmental goals, iPhone 13 Pro and iPhone 13 Pro Max do not include a power adapter or EarPods. Included in the box is a USB‑C to Lightning Cable that supports fast charging and is compatible with USB‑C power adapters and computer ports.
We encourage you to re‑use your current USB‑A to Lightning cables, power adapters, and headphones, which are compatible with these iPhone models. But if you need any new Apple power adapters or headphones, they are available for purchase.