If you updated recently, take a breath: the iPhone spends its first 24 to 48 hours rebuilding the search index, reprocessing the photo library and updating apps in the background. During that window it runs slow, gets warm and uses more battery, and it clears up on its own. Solution 1 explains how to speed that process along instead of fighting it. If more than two days have passed, start with Solution 2, which is restarting, and Solution 3, which is freeing storage: nearly full storage is the number one cause of lasting slowness. Solution 4 shows how to check battery health, because a worn battery makes the iPhone slow itself down on purpose. And if nothing works, Solution 8 has the reset that does not erase your data.
What causes this problem
- Normal reindexing work during the first 24 to 48 hours after updating, with photos, search and apps being reprocessed in the background.
- Nearly full storage, which leaves the system no room to manoeuvre for temporary files.
- Apps not yet updated for the new system version, running inefficiently or crashing.
- A battery with reduced capacity, which makes the iPhone limit performance to avoid shutdowns.
- Too many apps with background refresh and heavy widgets active at the same time.
- An older device receiving a system version designed for newer models, which shows up as constant slowness.
- Check how long ago you updated. Less than two days changes the diagnosis completely, and Solution 1 explains why.
- See whether the slowness is general or limited to one app. If it is one app, the problem belongs to that app and Solutions 5 and 6 fix it faster.
- Note your iPhone model. Older generations have a real performance ceiling, and that changes expectations.
- Start with at least half the battery, or plug the phone in. Some fixes restart the iPhone more than once.
- Make a backup before the fixes at the end of this guide, even though they do not erase data. It is quick and saves headaches.
Solutions, in the order to try them
1Give the iPhone its first 48 hours before touching anything
This is not advice meant to stall you: it is what actually happens inside. After installing a new system version, the iPhone has to rebuild the search index for the whole device, reanalyse the photo library to recognise faces and objects, migrate internal app databases and download updates for installed apps. All of that runs in the background and uses the processor, which leaves the device slow, warm and draining faster. It is normal and it passes on its own. What you can do is help that work finish sooner.
- Leave the iPhone charging and on Wi-Fi overnight, with the screen off. Most of that processing happens in exactly those conditions.
- Do not keep opening the Photos app during this period: the processing slows down while you are using the device.
- Leave automatic app updates on for those two days, so everything adjusts to the new version at once.
- If the device gets warm during this phase, that is expected. Take the case off and leave it on a hard surface while it works.
- After 48 hours, if it is still slow, move on to the next solutions. At that point the slowness has stopped being normal.
2Restart the iPhone properly
Restarting clears memory, ends processes that got stuck during the update and forces the system to reload everything from scratch. It is the simplest step and it fixes a large share of cases where slowness appeared out of nowhere. If the device is so frozen that it will not shut down the normal way, a force restart does the same without erasing anything.
- In Settings > General, scroll to the bottom and use the shut down option. Wait half a minute with the device off before turning it back on.
- If the screen does not respond, force restart: press and release volume up, press and release volume down, then hold the side button until the Apple logo appears.
- On models with a physical home button, the force restart is done by holding the home and side buttons together.
- After restarting, use the device normally for a few minutes before judging the result.
3Free up storage space
This is the number one cause of slowness that will not go away. The system needs free space for temporary files, cache and reorganising data, and when storage gets close to the limit it starts tripping over itself. After an update the effect is worse, because the new version usually takes more space than the previous one.
- Open Settings > General > iPhone Storage and wait for the chart to load completely.
- Aim to keep at least ten percent of the total free. Below that, slowness shows up even on new devices.
- That screen itself suggests actions, such as reviewing large videos and deleting old attachments from conversations. Start there, as they free the most space in the least time.
- Use the option to offload unused apps: it removes the app while keeping its documents and data, and the app returns to normal when you tap the icon.
- Empty the recently deleted album in the Photos app. It holds photos for weeks and takes real space.
- If most of the space is photos and videos, move them to a computer or a cloud service before deleting anything.
4Check the battery health
The iPhone reduces performance on purpose when the battery can no longer deliver the current it needs, so it does not shut down under peak load. That is visible on a specific Settings screen and explains cases of slowness that come with unexpected shutdowns or sudden percentage drops. It is not an update fault: it is an aged battery becoming obvious once the new system asks more of the device.
- Open Settings > Battery > Battery Health and Charging.
- Look at the maximum capacity. Values well below eighty percent point to a battery near the end of its life.
- Check whether a message about performance management being applied is shown. When it is, the device really is slowing itself down because of the battery.
- In that case, replacing the battery restores performance. Prefer an authorised or trusted repair shop, because batteries of dubious origin tend to bring the problem back.
- On the same screen, look at usage per app: one app far above the others usually explains the slowness and the short battery life at the same time.
5Update the apps and the system
After a new system version, developers publish fixes so their apps adjust. An outdated app can crash, consume too much and drag down the whole device's smoothness. And Apple usually releases smaller versions shortly afterwards, precisely to correct performance problems that showed up in the bigger one.
- Open the app store, tap your profile picture and update everything pending.
- In Settings > General > Software Update, install the most recent version available for your model.
- If the slowness is limited to one app, close and reopen it. If it persists, delete it and install it again, knowing you will have to sign in once more.
- Leave automatic app updates on: that way fixes arrive without you having to remember.
6Cut back what runs in the background
Background refresh, always-on location and widgets that fetch data constantly keep the processor busy even when the device is idle. On a new iPhone that barely registers, but on a device that is a few years old it makes a clear difference after an update, when the system already demands more.
- In Settings > General > Background App Refresh, turn off apps that do not need to refresh on their own. Messaging and email are worth keeping; games and shopping, less so.
- In Settings > Privacy and Security > Location Services, switch apps set to always to while using instead.
- Remove widgets from the home screen that you never look at. Each one fetches data periodically.
- If you run Low Power Mode all day, be aware it reduces performance on purpose. Turn it off and compare for a day.
7Make the interface lighter
The animations and transparency effects in iOS use graphics resources. Reducing them does not make the processor faster, but it cuts the time each animation takes and makes the device feel noticeably more immediate, which handles a good share of the sensation of slowness on older models.
- Open Settings > Accessibility > Motion and turn on reduce motion.
- In Settings > Accessibility > Display and Text Size, turn on reduce transparency.
- In that same section, if the text size is very large, try going back to the default: extreme sizes make the system recalculate the screen more often.
- If you use an animated or dynamic wallpaper, switch to a still image and compare the smoothness.
8Reset settings without erasing your data
There is a reset that returns every setting to its factory default without touching photos, messages and apps. It fixes cases where some setting became inconsistent during the update, and it is the safe step before thinking about restoring the whole device. The price is having to set preferences again: brightness, notifications, Wi-Fi passwords, wallpaper and accessibility settings go back to the original.
- Make a backup first, for safety, even though your data will not be erased.
- Write down the Wi-Fi passwords you use, because they are forgotten.
- Open Settings > General > Transfer or Reset iPhone > Reset and choose the option to reset all settings. Do not choose the option that erases content and data.
- Confirm with the device passcode and wait for the restart.
- Use the iPhone for a day before setting everything up again, so you can judge the performance with nothing added back.
9Last resort: restore the device from a computer
When nothing worked and the slowness is general, restoring installs the system from scratch and clears any leftover corrupted file from the update. It is the longest step and the one that needs the most care, because it erases the entire contents of the device before putting them back from the backup. Only do it with a confirmed backup and time to spare.
- Make the backup to the cloud or to a computer and confirm it finished, checking the date and time of the last backup.
- Check that you remember the password for the account used on the device. Without it, the iPhone will not grant access after the restore.
- Connect the iPhone to the computer and use the restore device option in the app that manages Apple devices.
- When it finishes, choose to restore from the backup.
- If you want to rule out a problem dragged along for years, set it up as new and reinstall apps gradually. It is more work, but it is the definitive test.
- If the device stays slow even freshly restored and empty, the limit is the hardware, and the battery replacement from Solution 4 is the last thing to try before considering a newer device.
Applies to
| System | Status |
|---|---|
| iPhone on iOS 17 and iOS 18 | Confirmed |
| iPhone on iOS 15 and iOS 16 | Confirmed |
| iPad on iPadOS | Every step applies; only the layout of the Settings screens differs |
| Older iPhone generations | The gain is smaller: part of the slowness is a real hardware limit, not configuration |
Menu names can change slightly between versions. If a step above does not match what you see on screen, the official support page from the manufacturer has the most current wording for your version.
Frequently asked questions
Last checked: Oct 12, 2026 · We review this guide whenever the manufacturer changes the process.