I've noticed that my phone charges much faster when I use the iPad Pro charger. They're both thunderbolt, so can I assume that I'm not damaging my phone?
I've noticed that my phone charges much faster when I use the iPad Pro charger. They're both thunderbolt, so can I assume that I'm not damaging my phone?
Yes, and they are Lightning ports not Thunderbolt ports. You could in general always use adapter capable to draw more current/power to charge, as long as voltage requirement is same. It just won't draw more charge than it needed.
Assuming you meant lightning rather than thunderbolt, yes, it's safe to use that adapter as the phone will draw whatever power it needs from it and no more (and will stop on its own when it no longer needs to charge).