Buying or Selling a Smart Device? Do a Factory Reset First

If you sell, give away or buy a smart device such as a camera, speaker, plug or thermostat, the first job is the same: do a factory reset. The UK government's smart-device guidance says a reset returns the device to its original settings and should remove your personal data. That is the step most people skip, and it is the one that stops your Wi-Fi password, your accounts and your habits from travelling with the gadget.

A smart device remembers more than you think, so wipe it before it leaves your hands and again when it arrives in someone else's.

Here is a plain routine for both sides of the deal, built on two government guides.

Why a reset matters when a device changes hands

A smart device is a small computer. It may hold your home Wi-Fi details, your account login and settings you have forgotten you made. If you sell it without a reset, the new owner could inherit all of that. If you buy one that was never reset, you may find it still linked to a stranger's account or set up in a way you did not choose.

The UK guidance gives two reasons to reset: before you sell or give a device away, and if you think someone else may have unauthorised control of a device in your home. How you actually do it depends on the model, so check the manufacturer's website.

Selling or giving one away: the checklist

The factory reset is the official advice. The other steps are common sense that I have added.

1. Remove it from your account in the app if the app allows it, so the device is no longer tied to you.
2. Do the factory reset using the steps on the manufacturer's site. It should remove your personal data.
3. Remove any memory card or attached storage if the device has one. This is my addition, not from the guides.
4. Take the batteries out if that is possible and appropriate.
5. Keep the original box and accessories together, which helps the next owner and helps the device sell.

Buying a used one: the checklist

The government pages do not have a section on buying second-hand, so what follows is my own reasoning built on their advice. A used device might not have been reset properly. Treat it as untrusted until you have set it up yourself.

That last point comes from the U.S. Cybersecurity and Infrastructure Security Agency (CISA). Its alert on new devices lists four steps: change default passwords, review security settings, apply patches as soon as possible, and consider whether the device needs a constant internet connection. A connected device is something an attacker can reach, so the fewer things you connect, the smaller the target.

What a reset does not fix

A factory reset deals with data on the device. It does not make an old device safe for ever. Two things to watch:

• Updates. A device that no longer receives updates will slowly become less safe. Before you buy, check whether the maker still supports it.
• Recalls. Smart plugs, heaters, chargers and cameras with batteries can be recalled for safety reasons. Our five-minute recall check works for these as well.

A few buying signs

When you are looking at a used device in person, which you can often do around the DC, Maryland and Virginia area, there are a few easy tests. Plug it in and see that it powers up. Check that the reset button works. Look at the label for a model number you can search. If anything about the device looks tampered with, or the seller will not let you test it, walk away. For help with pickup and what to expect, see our help page.

The bottom line

Reset before you hand it over. Reset again when it is yours. Change the default password, turn on updates and two-factor sign-in if offered, and ask whether the device really needs to be online. The steps take about ten minutes, and they close the most common gaps.

If a friend is about to sell an old smart speaker or camera, forward this to them first.