Why is my phone getting so hot and slow?

Most overheating is software or situational: a heavy app or game, a background app stuck awake, charging while using it, direct sun, or a post-update reindex. Heat makes the phone deliberately slow down (thermal throttling) to protect itself. Genuine hardware causes like an ageing battery are less common but real.

Is it normal for a phone to get warm?

Yes — noticeable warmth during gaming, navigation, video, camera use or fast charging is normal. It is a concern when the phone gets hot during light use or idle, gets too hot to hold comfortably, or shows a temperature warning screen.

Can a bad battery cause overheating?

Yes. A degraded or swelling battery can run hot and cause shutdowns. If battery health is low, or the back of the phone is bulging, that is a hardware cause that needs professional attention — a swelling battery is a safety issue.

How much does it cost to fix an overheating phone?

If it is software, it is free to resolve. If a worn or swollen battery is the cause, a replacement is roughly $69 to $149 at an Australian independent shop in 2026. Logic-board level thermal faults are rarer and need diagnosis to price.

Troubleshooting · Power

It runs hot and slows down.

Most overheating isn't a broken phone — it's software or situation, and the slowdown is the phone protecting itself on purpose. Here's how to tell ordinary heat from a real fault, and which causes actually cost money.

Key idea: when a phone gets hot it deliberately slows itself down — that's thermal throttling, a protection feature, not damage. So "hot and slow" is usually one problem (heat) causing the other (slowness). Fix the heat source and the speed comes back. Most heat sources are free to fix.

First: is this even abnormal?

Phones are supposed to get warm under load. Before troubleshooting, check this isn't normal heat:

Normal: warm during gaming, GPS navigation, video calls, camera/4K recording, fast charging, or for a day or two after a big OS update while it reindexes. Warm but usable = fine.
Not normal: hot during light use (messaging, browsing) or while idle in your pocket; too hot to hold comfortably; a temperature-warning screen; or hot and the battery draining unusually fast.

If it's the "normal" column, there's nothing to fix — the throttling is doing its job. If it's the "not normal" column, work through the causes below.

The common causes, free ones first

A heavy or stuck app (free)

The number-one cause. A game, a buggy app, or one stuck awake in the background pegs the processor and heats the phone. Open Settings → Battery and look at what's consuming the most. An app you barely use sitting at the top is the culprit — force-close or uninstall it and see if the phone cools and speeds up. This resolves a large share of cases for nothing.

Charging + using + environment (free)

Using the phone hard while charging (especially fast charging) compounds heat. So does direct sun, a hot car, or a thick case trapping heat. Take it off charge, out of the sun, off the case, let it rest a few minutes. If it cools fast and stays cool under normal use, that was it.

A settling update, or a software/malware angle (free)

Heavy heat for 1–3 days after a major update is usually post-update reindexing — let it settle and re-check. Persistent unexplained heat with battery drain can also be a misbehaving or malicious app, especially anything sideloaded on Android: review recently installed apps, remove anything you don't recognise or trust, restart. This is the ceiling of what software can do — if it's still abnormally hot after this, look at hardware.

The battery (this is the paid one)

A degraded battery runs hotter and can cause heat-related shutdowns. Check battery health (iPhone: Settings → Battery → Battery Health; Android: device care/diagnostics — see our battery guide). Low health plus persistent heat points to the battery. This is where it becomes a repair rather than a free fix.

Safety — don't ignore this one: if the back of the phone is bulging or swollen, the phone is hot to the point of being hard to hold, or it smells of chemicals, stop using and charging it and get it to a professional promptly. A swelling lithium battery is a genuine safety hazard, not a "deal with it later" issue.

What it costs to fix

It depends which cause you landed on:

Software / app / environmental: free — identify and remove the heat source.
Worn or swollen battery: roughly $69–$149 at a 2026 Australian independent shop for most models — and one of the best-value repairs, since it also restores battery life and stops the throttling.
Logic-board / thermal hardware fault: rarer; needs a proper diagnosis to price, and on an older phone may not be economical — a good shop will tell you honestly.

For your model's battery range, the cost calculator and model pages have specifics.

DIY, honestly

The genuine DIY here is all the free software/environment work above: find the heavy app, stop charging-while-gaming, take the case off, let an update settle, clear out untrusted apps. That fixes the majority of overheating with zero spend — do it before assuming the phone is faulty.

For a battery-caused case we won't walk through a replacement: modern batteries are glued in behind glued glass and a damaged or swollen lithium cell is a real fire risk to handle. A swelling battery in particular is a safety issue, not a DIY-curiosity repair. If the cause is the battery, this is a shop job — quick and cheap for a technician with the right tools, and the safety margin matters.

In Newcastle or the Hunter? If health is low or the battery's swelling, a battery replacement is one of the fastest, best-value repairs a local shop does — often same-day, and it ends the heat-and-throttle cycle. Our Newcastle repair guide has honest local pricing and a workshop we're comfortable pointing people to. A swelling battery is worth getting seen sooner rather than later.

Common questions

It's hot and slow — did I damage the phone?

Usually not. The slowness is deliberate thermal throttling to protect the phone from the heat — remove the heat source (usually an app or charging-while-using) and the speed returns. It's a protection feature doing its job, not damage.

It got hot right after an update — is that the cause?

Often it's post-update reindexing, which runs hot for 1–3 days then settles — give it that long and re-check before worrying. Occasionally an update ships a genuine bug a later patch fixes. Either way, let it settle first.

Could it be a virus or malware?

Possible, particularly with sideloaded Android apps — malicious software can peg the processor and cause heat plus drain. Review recently installed apps, remove anything untrusted or unrecognised, and restart. iPhones are far less prone to this but a misbehaving legitimate app can do the same.

The back of my phone looks slightly swollen — what do I do?

Treat that as urgent. A swelling battery is a safety hazard — stop using and charging the phone and get it to a professional promptly. Don't press on it, puncture it, or leave it charging unattended while you wait.

Next step

Software ruled out? It's likely the battery.

If health is low or it's swelling, replacement is cheap, fast and ends the heat-and-throttle cycle. Check your model's range.

Open the cost calculator Other symptoms