Will using a Samsung 25W charger affect iPhone 16 Pro Max battery health?

A compatible high-power USB Power Adapter is completely safe to use with your iPhone; providing that the Power Adapter itself is healthy, it will not cause any issues whatsoever. That said, if a fault were to occur, the Power Adapter has the capacity to cause considerable damage to low-power electronics.

Apple’s current range of Power Adapter’s support USB PD (Power Delivery). USB PD is an active protocol; the source (Power Adapter) and sink/load (in this case, your iPad Pro) “negotiate” and agree a common Power Profile that will determine the charging voltage that will be applied.

You should note that non-PD compliant Power Adapters may not provide more than 12W to charge your iPhone. For non-PD power sources, or compliant devices that fail to negotiate a mutually supported Power Profile, the Power Adapter will only supply the standard USB 5V at a reduced current (typically 2.4A @5V). This mechanism is intended to ensure that the higher charging voltages not supported by non-PD devices are not damaged by an over-voltage condition.

Maryam_k2748 wrote:

Yeah, the adapter.

I wanted to know if it is necessary to buy the apple adapter or other brands are suitable as well?

No it’s not necessary. I’m sure it’s a good enough adapter. Also it supports Fast Charging, it being a 25W adapter so that’s good.

the phone would not know the difference

Hello!

Do you mean the adapter that plugs into the wall? I don’t know of any reason why it should damage the battery.