"iPhone won't charge" is one of the few problems where the most likely explanation is that nothing is broken at all. Modern iPhones pause, slow, or interrupt charging on purpose — to protect the battery from heat and from sitting at 100% for hours. Telling protection apart from a real fault is the whole skill here.
Slow, or stopped at 80%: usually designed behaviour
Two deliberate behaviours account for most complaints:
Optimized Battery Charging. The phone learns your routine. Overnight, it charges to about 80%, then waits, finishing to 100% shortly before you normally unplug. If you plug in at 11pm and check at 2am, seeing 80% is exactly right. You can see whether it is active under Settings → Battery → Battery Health & Charging. To finish now, long-press the charging notification and pick Charge Now.
Charging on Hold (temperature). When the battery gets too warm, iOS pauses charging and says so on screen. Heat is the single biggest cause of battery aging, so this is protection doing its job — see Screen Dims / Charging Paused: Heat Protection. It resumes by itself once the phone cools. The usual triggers are direct sun, charging under a pillow or blanket, a thick case, or heavy use while plugged in.
How to tell protection from a fault: if removing the heat source or waiting resumes normal charging, it was protection. If the phone is at room temperature, idle, and still will not charge, keep reading.
Check in this order: cable → charger → port
Real charging faults are usually mechanical, and the order matters because it goes from most likely to least likely.
1. The cable. Cables fail far more often than chargers. They break inside at the connector and at the bend, often invisibly. Swap in a known-good cable first — this one step resolves a large share of cases. Cheap uncertified cables also fail to negotiate fast charging, which looks like "charging is suddenly slow".
2. The charger. Try a different one, ideally a different wattage. A 5W adapter charges an iPhone slowly by design — if you moved a charger between devices, you may simply be using a weak one. Fast charging needs a USB-C Power Delivery adapter of adequate wattage, and the phone picks the highest rate both ends support.
3. The port. Look into it with a light. Pocket lint, dust, and fabric fibres pack against the contacts and stop the connection from seating. This is one of the most common causes of a phone that "suddenly won't charge" — and it is usually visible. Clear it gently with a wooden toothpick or a soft dry brush; never metal, and never liquid.
4. Cross-check wireless against wired. If wireless charging works but wired does not, the fault is in the wired path: cable, adapter, or port. If neither works, the problem is on the phone side — port hardware or battery — and that is a repair.
5. Then, and only then, consider the battery. Settings → Battery → Battery Health & Charging — a battery below 80% may not hold voltage well, but note that a worn battery usually shows up as fast *drain*, not as inability to charge. See Battery Health Explained.
Why wireless is slower, and what "charging while playing" really costs
Wireless charging is inherently less efficient. Energy lost in the transfer becomes heat, and heat triggers the throttling above — so wireless charging is slower not only because of the transfer itself, but because the phone keeps protecting itself along the way. Alignment matters more than people expect: a case that is too thick, or a phone sitting slightly off-centre on the pad, drops the rate sharply.
Charging while gaming or navigating means the phone is charging and discharging at once, and both ends of that produce heat. The practical costs are: it charges slowly or not at all, it gets genuinely hot, and sustained heat is what ages the battery. See Why Charging Makes Your Phone Hot. If you must charge during heavy use, taking the case off helps more than most people expect.
Four things that are not true
- "Charging slowly means the battery is dying." It almost never does. Cable, adapter, port, and temperature explain the overwhelming majority of slow-charging reports.
- "You must use the original charger." What matters is the standard (USB Power Delivery) and build quality, not the brand stamped on it. An uncertified no-name adapter is a real risk; a reputable third-party adapter is not.
- "Wireless charging damages the battery." The wireless part is not the issue — the extra heat is. If it stays cool, it is fine.
- "Charging overnight ruins the battery." Modern iPhones do not overcharge. What ages a battery is spending hours held at 100%, which is exactly what Optimized Battery Charging exists to reduce — and if you want more control, a charge limit does it explicitly: Charge Limit: Is 80% Worth It?.
When to stop troubleshooting and get it looked at
Go to Apple or an authorised provider if: the port is visibly damaged or the cable does not click in; the phone will not charge on any cable, adapter, or wireless pad; the connector gets hot enough to be uncomfortable; or the phone only charges when the cable is held at a particular angle. Those point at hardware, and no amount of setting-tweaking will fix them.