iPhone SE gets quite hot after replacing the protector casing I recently bought a new iPhone SE case, a silicone one in book style from B2CTelecom. The particular one I bought in case it matters is https://www.bol.com/nl/p/iphone-se-5s-5-standcase-hoesje-design-stars/9200000104229975/

I've found that while watching online videos like Youtube and Twitch, it gets quite hot after about half an hour to an hour. is this because of the new case acting too much as an insulator? Could this end up damaging my iPhone? The iPhone was bought new in 2016, and the battery max capacity right now is at 91% according to the settings app.
Use iOS devices where the ambient temperature is between 0º and 35º C (32º to 95º F).

source: https://support.apple.com/en-us/HT201678
Some of the reasons I can think of:

Not having proper ventilation around the phone. Even though this is a prominent thing for laptops, phones also need to dissipate heat.

Low cellular connectivity. Poor Wi-Fi won't heat up the iPhone much, but cellular is the main culprit if it's poor. (personal experience)



When you use graphics-intensive or augmented-reality apps or features.

Which you're doing.  Camera also falls under this(personal experience).


If device overheats, some features will underperform, like flash or camera, dimming of display and other graphic intensive tasks. It might even get locked if temperature goes beyond a threshold.