Why you can trust ZDNET
:ZDNET independently tests and researches products to bring you our best recommendations and advice. When you buy through our links, we may earn a commission.Our process
'ZDNET Recommends': What exactly does it mean?
ZDNET's recommendations are based on many hours of testing, research, and comparison shopping. We gather data from the best available sources, including vendor and retailer listings as well as other relevant and independent reviews sites. And we pore over customer reviews to find out what matters to real people who already own and use the products and services we’re assessing.
When you click through from our site to a retailer and buy a product or service, we may earn affiliate commissions. This helps support our work, but does not affect what we cover or how, and it does not affect the price you pay. Neither ZDNET nor the author are compensated for these independent reviews. Indeed, we follow strict guidelines that ensure our editorial content is never influenced by advertisers.
ZDNET's editorial team writes on behalf of you, our reader. Our goal is to deliver the most accurate information and the most knowledgeable advice possible in order to help you make smarter buying decisions on tech gear and a wide array of products and services. Our editors thoroughly review and fact-check every article to ensure that our content meets the highest standards. If we have made an error or published misleading information, we will correct or clarify the article. If you see inaccuracies in our content, please report the mistake via this form.
Here is thermal imaging comparing the iPhone 15 Pro Max and the Samsung Galaxy S23 Ultra. This suggests that the iPhone's lack of active cooling is concentrating the heat in a specific spot.
Then there's chip performance throttling. This test suggests that in two minutes of heavy loading, the iPhone lost 25% of its performance. This would point to a thermal management issue.
The common thread in many of these reports seems to be USB-C charging. Maybe there's a bug here that surfaces under certain conditions or with certain charging hardware.
Another option is that the titanium chassis is more effective at dissipating the heat, and this in turn causes the handset to feel hot. But aluminum and stainless steel are also good conductors of heat, so I doubt that the material is the issue.
ZDNET has not come across this issue in our testing but there's no doubt that these measured temperatures are abnormally high.
Note that while 42°C/107°F is hot, it's within the safe "no injury" temperature range. In fact, ASTM C1055 (the Standard Guide for Heated System Surface Conditions that Produce Contact Burn Injuries) states that the average person can touch objects up to 60°C/140°F for up to five seconds without sustaining irreversible burn injuries.
Anything that seems to trigger it?
I've seen a few different theories.
First theory is a rogue app. Faruk Korkmaz of the YouTube channel iPhonedo puts the problem down to the Instagram app, and he's done tests to show just how quickly the iPhone overheats when this app is running on his hardware.
Another theory is that it is related to fast charging, with Android Authority noting that the overheating happens when using a 65W USB PD GaN charger, but goes away when using a 15W USB PD charger, but that charging time is significantly longer.
I've seen a lot being made of the fact that thermal imaging shows this heat to be concentrated around the location of the iPhone's mainboard, which would suggest that the heat coming from the A17 Pro chip. That said, thermal imaging of devices through the case can be hard to interpret because the location where the heat is being dissipated might not be the location where it is generated.
Is this a bug?
History shows that both new iPhones and new iOS releases are prone to bugs that are fixed by subsequent iOS updates.
While it's easy to point the finger at charging (but remember, all smartphones get warmer when charging -- that's just physics), the throttling of the chip points more to a thermal management issue. Apple is either dealing with a software bug or needs to improve the way the iPhone operates when running heavy workloads.
This could also be something specific to certain handsets or a configurational issue resulting in an abnormally high level of background activity, such as machine learning or indexing.
This issue is likely a software issue, and will be fixed by a future software update from Apple or an app update.
My iPhone is overheating! What should I do?
The fastest way to cool down an iPhone is to turn it off completely and let it come down to normal temperature naturally. Don't try to speed up the process by putting the iPhone into a refrigerator or ice box as this could also damage the battery.