All computing devices are prone to slowing down over time, as their memory fills up and extra software is installed, but the way iPhones use their memory makes them less prone to this than most.
It's possible that it just feels slower than it used to, because you've got used to what initially seemed dazzlingly quick operation, or have started to compare it to friends' newer, faster models.
But sometimes it's possible to make a direct comparison: when there's an app you used to enjoy but has since become unusably juddery. Such a situation is what led us to write this feature. The wonderful, super-fast game Super Hexagon demands lightning reflexes to survive, but the stuttering graphics on our iPhone 4 now make it impossible to play. We've also been seeing problems with the iPhone 4 handling Temple Run 2.
Here are some great methods to speed up an iPhone 3GS, iPhone 4, iPhone 4S or even iPhone 5, iPhone 5c or iPhone 5s, if you're not happy with the way it's running.
1. Keep your iPhone up to date
Apple's most recent operating system for the iPhone and iPad is iOS 8. On older smartphones, it's possible that upgrading will slow down your iPhone a bit, but on some occasions it may even help it run faster. (The iPhone 4 and earlier aren't compatible with iOS 8 upgrades at all).
Check whether your iPhone is up to date by heading to Settings > General > Software update.
2. Shut down all open applications
Let's start with the easiest solution: closing down all non-essential apps.
Double-click the Home button to bring up the currently running apps in iOS 7 or later. Swipe upwards to close them. You can swipe with up to three fingers to speed up the process a little bit. Irritatingly, there's no way to close them all at once. We're going to close down everything, then start again from scratch.
3. Reallocate the memory
The iPhone 6 and 6 Plus have 1GB memory, but older phones have even less. Apple doesn't make reallocating this RAM type memory easy but there is a way you can do this and therefore speed up your iPhone.
Download the free Battery Doctor app. We use this primarily to reallocate our memory on our iPhone. If you find that you're using up lots of memory, tap 'Boost' and watch as the app reallocates the memory and helps speed up your phone.
We're not sure how long this app will stick around, as it seems that the memory feature has been removed in the past before reappearing in new versions of the app. It's possible that Apple isn't keen on apps that allow you to reallocate the RAM.
Hopefully Apple will make memory handling better in the future.
Let's restart the iPhone completely. Press and hold the Sleep button (the one on the top right of the iPhone) until the Power Off slider appears. Swipe it and wait for the iPhone to power down.
Once it's finished (it'll take about 10 seconds or so), start the iPhone up again by pressing and holding the Sleep button for about 5 seconds. You'll see the Apple icon for a minute or so, then the iPhone will restart.
You shouldn't have to do this very often, but when you do it'll clear out the memory space and can often fix unruly apps. The occasional power cycle helps keep iOS ticking over.
5. Delete apps
Delete apps you don't need by going to settings, general, usage and then tapping manage storage. You'll now see a list of apps and how much space they are taking up on your phone. You should aim to have at least 1GB space left, so delete any apps you don't need by tapping on it, and then tapping delete app.
6. Clear your Safari cookies and data
Let's try emptying Safari's data, cookies and so on to free up some memory. Open the Settings app and scroll down to Safari. Here you can choose Clear History and Clear Cookies and Data. (Bear in mind, though, that Safari will no longer suggest URLs as you type, unless they're bookmarked. And clearing the data may mean some websites forget your preferences.)
7. Kill automatic background processes
Getting rid of automated features will help keep your iPhone running faster in iOS 7 and iOS 8, and help extend your battery life as well. If you're running iOS 6, you can skip this step as Apple didn't introduce these features until iOS 7.
Turn off Automatic Downloads. Tap Settings > iTunes & App Store > and turn Automatic Downloads off. If you spend a lot of time uploading Music, Apps and Books you might want to turn off those as well.
Turn off Background App Refresh. Tap Settings > General > Background App Refresh. Turn Background App Refresh off and tap Disable Background App Refresh.
Both of these are luxury items. You don’t need them and you’ll see a big boost in battery life as well as a noticeable increase in performance.
8. Turn down the graphics
Again, iOS 6 users can skip this step because it only relates to iOS 7 and iOS 8, which introduced some fancy new visual effects.
Turn off Motion. Tap on Settings > General > Accessibility > Reduce Motion and set Reduce Motion to On. This turns off the parallax effect of icons and alerts (many people find it easier to use in this setting).
Increase Contrast. Tap on Settings > General > Accessibility > Increase Contrast and set Reduce Transparency to On. This disables the see-through background effects, which speeds up iOS 7 and iOS 8. It’s most noticeable on Control Centre which will now have a solid background and should work much faster.
Both of these will help with battery life, but are especially helpful for speeding up iOS 7 and iOS 8.
9. Delete text messages
We'll continue on our quest to free up memory by going through the Messages app and deleting everything that we don't need to save.
Open Messages and scroll down to find any message threads that you can manage without. Swipe to the right and tap Delete.
10. Delete unnecessary songs, photos and videos
Okay, let's get serious and free up a lot more memory. Open the Settings app, then tap General, and Usage like you did when we were uninstalling apps. You'll see how much storage space is left and which apps are using up most of the space.
If you're anything like us, the top two culprits will be Music and Photos & Camera, because these apps' storage usage includes music, images and videos. We'd suggest keeping at least 1GB free just to make sure there's some free space for iOS to shunt files around without having to do too much juggling.
Open the Music app and find the non-vital track, album or artist that you want to delete. Swipe to the right and press Delete.Some song duplicates in your iPhone would also occupy a large amount of storage. You could delete song duplicates in iTunes and then sync to your iPhone freely.
Plug the iPhone into the Mac and open Image Capture (assuming you've not set it to open automatically when it detects an iOS device). Tick the option 'Delete after import' at the bottom left.
Click the photo you want to copy across, or select multiple consecutive photos using the Shift key, and drag and drop them into a folder on the Mac. You'll see a green tick appear next to them in Image Capture, to show that they've been downloaded.
If there are any photos on there that you don't want to keep but still want deleted from the iPhone, select them and click the red circle at the bottom. Image Capture will confirm you want to delete the photo.
Of course, you can also delete photos on the phone itself. Open the Photos app, find the images you want to delete, tap 'Select' and then tap on the images you want to delete. The tap the bin icon and confirm to delete the photos and videos you've selected.
Related reading: How to Erase Photos from iPhone with iOS 8
A more drastic step than restarting the iPhone, a full reset takes longer but is a more effective way of solving problems with the way an iPhone is running.
Press and hold the Home and Sleep buttons at the same time. Keep holding them while the screen goes black (the red power-off slider may appear; if it does, just carry on holding the buttons), right up until the silver Apple logo appears. When that appears you can let go.
12. Restore from backup
The next stage after resetting the iPhone, getting steadily more drastic as we go, is restoring it from a backup.
If you've backed up recently, you can simply restore from that. Plug the iPhone into the Mac and open iTunes.
Click the iPhone (if you've plugged in more than one iOS device it may say '2 devices' or similar instead). Under Backups, click 'Restore Backup...'.
(To back up your iPhone into iTunes, click the Back Up Now button next door.)
Of course, that's going to undo all of the changes you just made to your device (deleting apps, removing unwanted music etc), unless you backed up your iPhone afterwards.
13. Restore to factory settings
Finally, the most drastic step of all: we're going to perform a full restore, which deletes all the data on the iPhone and returns it, in effect, to the state it was in when you bought it. (Except that the hardware components will still have suffered a number of years of wear and tear, of course.)
Since we're deleting all the data, it's vitally important that you back up the iPhone: either back up to iTunes, as described above, or to iCloud. (To back up to iCloud, Open the Settings app, then scroll down to iCloud, then Storage & Backup, then Back Up Now in iOS 6 or turn on iCloud Backup in iOS 7 and iOS 8).
Now you can restore the iPhone to its factory settings by going to Settings, General, Reset, Erase All Content and Settings. You'll then have to enter your passcode if you've got one, and then confirm that you want to delete all media and data, and reset all settings.
After a few minutes of restoring, you'll be presented with the welcome screen you saw when you first started up the iPhone.
14. Check your warranty, and make an appointment with Apple
If none of the above techniques work, it's time to decide whether the speed of your iPhone is a serious enough problem for you to take it up with Apple. If there's a problem with a component, the issue may be covered by your Apple warranty if you have one - see 'Will Apple replace my iPhone?' for more on your legal rights.
However, as we mentioned above, slowness can be a matter of perception; but if you're sure something's up, and you've tried all our tricks, you may wish to ask Apple if they can check for a hardware issue.
If you’ve tried all of these ways and found it hard to speed up your iPhone, or, if Apple can't help or their help is too expensive to be worth it, you may have the last option: give up on your older iPhone and buy something newer.