Your phone gets hot: harmless or a warning sign?

Every phone gets warm under load, that is physics and not a defect. It gets interesting when the device becomes hot without you doing anything demanding with it. Then it is worth narrowing things down systematically.

When warmth is completely normal

• While navigating with a bright display and active GPS.
• While charging, especially with fast charging and wireless charging.
• When recording video, gaming or on longer video calls.
• In the first few hours after setting up a new device, while photos and apps sync in the background.

In all these cases the device feels warm to uncomfortably warm, but cools down again once the task is finished. If your phone warns you with a heat notice and dims the display, that is self-protection and works exactly as intended.

When it is not normal

It becomes suspicious when the phone gets hot while idle, when the battery drains unusually quickly, when it gets very hot while charging or when the housing or the display bulges. The last point is clear cut: a swollen battery is a safety risk. Stop charging the device, switch it off and take it to a workshop.

How to narrow down the cause

1. Check the battery usage: in the settings you can see which app draws how much energy. If an app you barely use is near the top, it is the most likely cause.
2. Restart: a background process left hanging is surprisingly often the reason. A restart costs one minute.
3. Take the case off: thick cases trap heat, especially while charging.
4. Test another charger and cable: a faulty cable creates contact resistance and with it heat, more on that in our post on cheap charging cables.
5. Install updates: after major system updates there are occasionally bugs that get fixed by a further update.

When the battery is to blame

An ageing battery has a higher internal resistance, and that resistance turns into heat. The typical picture is a hot device, fast discharge and sudden shutdowns while the charge level is still in double digits. If the battery health is below 80 percent, that connection is likely. A battery replacement then clears up several symptoms at once. Whether that is worth it or whether replacing the device makes more sense is something we worked through here.

Conclusion

Warm under load is normal, hot while idle is not. Work through the list from top to bottom, that costs ten minutes and clears up most cases. With a bulging housing there is only one correct response: stop charging and go to the workshop.