Watching videos for long time
Watching YouTube or Netflix for season-long sessions is just as detrimental to your phone’s health as marathon gaming.
Gaming for long periods of time
Much like PCs, gaming on a smartphone takes the CPU and GPU to their limits, which causes them to generate a lot of heat.
App and OS issues
Certain bugs in apps and your OS can cause your phone to overheat or misbehave.
Malware can heat your phone
Since malicious apps are usually unoptimized pieces of code, they uses your phone’s CPU and memory, throttling them and generating a lot of heat. One of the main reasons is cryptojacking.