Does closing all the apps in the app switcher help?

Only in the moment. The phone manages memory itself and puts apps to sleep when they are not in use. Swiping every app away each day makes no difference over time, though it does help when one particular app has frozen right now.

Does Apple slow phones down on purpose when a new model comes out?

No. What happens is that an iPhone lowers its speed when the battery is worn, so the phone does not shut itself off. Replacing the battery removes the slowdown. You can see the battery condition under Battery Health and Charging.

Do I need an app that cleans up my phone?

No. Those apps rarely help, show adverts and can make the phone slower. Everything you need is already built into the phone under Storage and Apps. Never pay for a cleaner or a driver updater.

When is a factory reset worth doing?

Last of all, and only with a backup you have checked and the password to your Apple account or Google account in hand. Without that password the phone can lock you out after the reset. Ask us before you do one.

Phone running slow? How to make it quick again

A phone that has become sluggish is rarely worn out. It is nearly always full storage, a system that has not been updated in a long time, or a battery that is getting tired. Restarting the phone and freeing a few gigabytes fixes it in most cases, and takes about fifteen minutes.

Start with the cheapest step: restart the phone. Many phones have not been switched off for months, and a restart clears whatever has got stuck without deleting anything.

Try this first

Restart the phone and leave it alone for a minute before you start using it again.
Check the free space. On iPhone: Settings > General > iPhone Storage. On Android: Settings > Storage, or on Samsung, Settings > Battery and device care > Storage. If less than ten percent is free, that is the most likely cause.
Free up space if you need to. Empty the bin in Photos or Google Photos, remove downloaded films and podcasts, and delete apps you never open.
Update the system. iPhone: Settings > General > Software Update. Android: Settings > Software update. Keep the phone on the charger and on Wi-Fi while it runs.
Update your apps. iPhone: open the App Store, tap your profile picture and choose Update All. Android: open Google Play, tap your profile picture and choose Manage apps and device.
Use the phone for a day and see how it feels. These four steps are enough for most people.

If that did not help

Check the battery on iPhone: Settings > Battery > Battery Health and Charging. Below 80 percent the battery is worn, and the phone then lowers its speed on purpose so it does not shut down. A battery replacement makes the phone noticeably faster and costs a fraction of a new one.
On Android, clear the cache for the apps that feel slowest. Settings > Apps > the app > Storage > Clear cache. This deletes nothing you have saved. Leave Clear data alone.
Look for apps working hard in the background. iPhone: Settings > Battery, and read the list at the bottom showing which apps used the most. Android: Settings > Battery > Battery usage. If it is an app you rarely open, remove it.
Turn down motion effects if the screen feels slow. iPhone: Settings > Accessibility > Motion > Reduce Motion. Android: Settings > Accessibility > Remove animations.
Remove widgets and live wallpapers from the home screen if you have several.

A factory reset does sometimes help, but it erases everything on the phone. Never do one before you have a backup you have checked, and before you know the password to your Apple account or Google account. Without it you can end up locked out of your own phone afterwards. If the phone restarts by itself, gets very hot, or is still slow after updating and clearing space, write to us and we will look at it together before you do anything that cannot be undone.