If your iPhone feels slower than it used to, you’re not imagining it — and you’re not necessarily being nudged towards a new device. iPhones slow down for real, specific, fixable reasons, and most of the time those reasons have nothing to do with the hardware itself being worn out.
There’s a persistent myth worth addressing directly: for several years, Apple was deliberately throttling older iPhones with degraded batteries to prevent unexpected shutdowns, through a feature called Performance Management. When this came to light in 2017 it caused significant controversy. Apple has since been much more transparent about it, and the key thing to understand is that Performance Management only activates when the battery is genuinely degraded — and it goes away when you fit a new battery. If your iPhone is slow, the battery is the first thing to investigate.
Here’s a methodical approach to diagnosing and fixing a slow iPhone, starting with the most impactful steps.
Step 1: Check Battery Health First
This is the most important diagnostic step, and it should always come first.
Settings > Battery > Battery Health & Charging
You’ll see a percentage — 100% when the phone is new, declining over time with use. Apple’s own guidance is that below 80% the battery should be replaced. In our experience at GenioTech, phones start to show noticeable slowdowns below 85%, particularly under heavy use.
You’ll also see whether “Performance Management” has been applied. If that notice is present, it means iOS has already determined that the battery can’t support full performance and has throttled the processor accordingly. Fitting a new battery removes this throttle immediately and completely — and the difference is dramatic. Many customers who bring in an iPhone 11 or 12 for a battery replacement report that it feels faster than it has in years.
If your battery health is below 80%, skip ahead to book a battery replacement. Everything else on this list still helps, but the battery is the big one.
Step 2: Free Up Storage Space
iOS behaves differently depending on how much free storage is available. When storage is nearly full, iOS can’t manage its caches, can’t write temporary files properly, and overall performance degrades. Apple recommends keeping at least 1-2GB free at all times — we’d suggest aiming for more.
Check your storage: Settings > General > iPhone Storage. You’ll see a coloured bar showing what’s using space, and a list of apps sorted by size below.
The biggest space consumers are almost always:
Photos and videos. Every phone user accumulates these. If you use iCloud Photos, your full-resolution photos are in the cloud and your iPhone keeps smaller local versions — check that iCloud Photos is turned on in Settings > Photos. If it’s off, your phone is storing every photo in full resolution locally.
Large apps and games. Some apps are surprisingly large. In the iPhone Storage screen, you can “Offload” an app — this removes the app itself but keeps its data, so if you reinstall it later you pick up where you left off. The icon stays on your home screen with a small cloud symbol.
Enable Offload Unused Apps automatically: Settings > General > iPhone Storage > scroll to “Offload Unused Apps” and enable it. iOS will automatically offload apps you haven’t used in a while, freeing space without you having to manage it manually.
Step 3: Turn On Reduce Motion
iPhones are full of fluid, attractive animations — apps zoom in when you open them, notifications swoop across the screen, the background parallax effect shifts as you tilt the phone. These effects are lovely, but they consume processing power, and on an older device or one under any performance management, they make the UI feel slower than it is.
Settings > Accessibility > Motion > Reduce Motion — turn this on.
When Reduce Motion is enabled, animations are replaced with simpler cross-fades. The phone still looks clean and functional — it just moves differently. On older devices, this change alone can make the UI feel noticeably snappier in everyday use.
Enabling Reduce Motion also automatically turns on Reduce Transparency, which simplifies some of the blur effects used on app switcher backgrounds and notification centres — another small performance gain.
Step 4: Turn Off Background App Refresh for Apps That Don’t Need It
Background App Refresh allows apps to update their content while they’re not actively open. The idea is that when you open an app, the content is already fresh. In practice, most apps handle this fine when you open them, and the background refreshing just consumes CPU cycles and battery in the meantime.
Settings > General > Background App Refresh
You can turn it off entirely, or turn it off selectively. We’d suggest leaving it on for apps where you genuinely want up-to-date content ready immediately — your news app, perhaps — and turning it off for everything else. Games, utilities, banking apps, and most productivity apps have no need to refresh in the background.
Step 5: Restart Regularly
iOS manages memory well, but even iOS benefits from an occasional fresh start. If you never fully restart your iPhone — just lock it and unlock it — memory pressure builds up over days of use. Apps that were “closed” aren’t always fully terminated; they sit suspended in RAM, and the more of them accumulate, the less headroom iOS has for the apps you’re actively using.
A weekly restart takes about a minute and keeps things running cleanly. Hold the side button and a volume button together (iPhone X and later) and slide to power off, then switch back on.
Step 6: Keep iOS Updated
iOS updates frequently include performance improvements, not just new features and security patches. Apple’s engineers continue to optimise iOS for older hardware with each release, and some updates specifically address performance issues that have been identified on particular devices.
Settings > General > Software Update
If there’s an update available, install it. Contrary to another common myth, updating iOS on an older phone doesn’t always make it slower — it very often makes it faster, or at worst has no noticeable effect. The version you’re already on is more likely to have the performance bug than the updated one.
Step 7: Reset All Settings
This is different from a factory reset, and it’s an important distinction. Resetting All Settings does not delete your photos, apps, contacts, or any of your data. It resets your phone’s preferences and configuration back to defaults — Wi-Fi passwords, display settings, keyboard shortcuts, privacy settings, notification settings.
Why does this help? Over time, corrupt or conflicting preference files can cause mysterious slowdowns, particularly if you’ve had the phone through multiple iOS updates. A settings reset clears all of that out while leaving your data completely intact.
Settings > General > Transfer or Reset iPhone > Reset > Reset All Settings
You’ll need to reconnect to Wi-Fi networks and reconfigure a few preferences afterwards, but your photos, apps, and personal data are untouched. Many stubborn slowdowns respond to this fix when nothing else has worked.
Step 8: Factory Reset as a Last Resort
If nothing else has worked, a factory reset returns the phone to completely fresh out-of-box state. This resolves any software corruption, accumulated junk, or configuration problems — but it does mean setting the phone up again from scratch.
Before doing this, make sure you have a recent iCloud backup: Settings > tap your name > iCloud > iCloud Backup > Back Up Now. Wait for it to complete.
Settings > General > Transfer or Reset iPhone > Erase All Content and Settings
After the reset, you can restore from your iCloud backup during the setup process, which brings back your apps, photos, and most settings. Think of it as a deep clean — the phone starts fresh, then your data flows back in.
The Battery Is Almost Always the Answer
In our experience repairing iPhones daily at GenioTech, the overwhelming majority of slow iPhones come back to the battery. A degraded battery causes Performance Management, which throttles the processor. It also means the phone runs hot more easily, which triggers further throttling. A new battery costs a fraction of a new phone and typically makes a dramatic and immediate difference.
If your iPhone is still sluggish after working through these steps, come into GenioTech at 29 Hilltown, Dundee for a free battery health check. We’ll check the health, run you through what we’re seeing, and give you an honest view on whether a replacement will help. We’re open Monday to Saturday, 9am to 5pm — walk-ins always welcome, or book ahead online if you’d prefer.