Warm is normal, hot needs a reason
Charging, fast charging most of all, warms the battery. So do games, video calls, navigation with the screen on, recording 4K video and long hotspot sessions. Apple designs the iPhone to work in ambient temperatures between 0° and 35° C (32° to 95° F); in a hot car or direct sun, the phone reaches its limits quickly whatever it is doing.
Heat with no obvious cause — in a pocket, screen off, not charging — is the case worth investigating, and the sections below go through it in order.
After an update, give it a day
For a day or two after an iOS update, or after setting up a new phone from a backup, the iPhone re-indexes photos, messages and files and downloads everything from iCloud. It runs warm and the battery drains faster while that happens. Leaving it on charge overnight on Wi-Fi lets the work finish.
If you are running a beta, debugging code and unfinished features add their own heat; our beta overheating guide covers that case.
Find the app responsible
Settings → Battery shows which apps used the most power over the last 24 hours and the last 10 days. An app near the top that you barely opened — especially one with a lot of background activity — is the likeliest source of heat. Updating it, or deleting and reinstalling it, usually stops it.
Background App Refresh, location access set to Always, and apps stuck uploading to their own cloud are the usual culprits. What drains an iPhone battery goes through each.
When it says the iPhone needs to cool down
The Temperature: iPhone needs to cool down before you can use it screen means the phone has protected itself. Move it somewhere cool and shaded, take it out of its case, and let it cool on its own. Do not put it in a fridge or freezer: condensation inside the phone does more damage than the heat.
Before it reaches that point, the phone dims the screen, pauses charging, slows the processor and weakens the cellular signal. All of that is reversible and stops once the phone cools.
While charging
Charging that pauses with a notice about temperature is the phone protecting the battery. Charging on a soft surface such as a bed or sofa traps heat; charging in a thick case on a wireless pad does the same. A hard surface and a case removed for wireless charging both help.
Uncertified cables and adapters can also run hot. If the heat is concentrated at the port or the plug, switch to an Apple or MFi-certified one.
When it is hardware
A phone that is hot with the screen off and nothing running, a battery that is visibly swollen — the screen lifting at an edge — or heat concentrated in one spot of the back are all signs of a battery fault. Stop charging a swollen battery and have it replaced. Settings → Battery → Battery Health shows whether iOS already considers it worn; see how to check battery health and when to replace it.
Frequently Asked Questions
Why is my iPhone getting hot?
Usually charging, gaming, video, navigation or the work iOS does after an update. Settings → Battery shows the app responsible when there is no obvious reason.
Is it normal for an iPhone to get hot while charging?
Warm, yes, especially with fast or wireless charging. Charge on a hard surface and take thick cases off; if it pauses for temperature, it is protecting the battery.
Can I put my iPhone in the fridge to cool it?
No. Condensation can form inside it. Move it somewhere cool and shaded, out of its case, and let it cool on its own.
Why is my iPhone hot after an update?
It re-indexes photos and files and syncs with iCloud for a day or two. Leave it charging on Wi-Fi overnight and it settles.