Before buying a used smart device, confirm the maker still supports it with security updates. When it arrives, factory reset it, then turn on automatic updates and set a strong lock or password. A cheap device with no remaining support is not a bargain.
Before you buy
- Check update support. The NCSC advises choosing a model the manufacturer still supports and avoiding models whose support is ending soon. Unsupported phones miss security updates.
- Compare the support end date with what you pay. A device with a year of support left costs more per month than a new one.
- Check the online purchase safety advice if you are buying online.
- Ask the seller whether the device has been reset and whether it is still tied to their account.
When it arrives
- Factory reset it. The NCSC says this removes the previous owner's messages, contacts, photos, passwords and apps.
- Complete the security setup. Turn on automatic updates and set a screen lock, password, PIN or biometric.
- Enable automatic backups, so future device switches are easier.
- Change any default or remembered passwords, and sign in with your own account.
Smart home devices
The NCSC page is written for phones and similar devices, but the same logic applies to cameras, speakers and plugs. A camera you buy used may still be linked to the previous owner's account. If you cannot remove that link, return the device. Do not use a device that someone else can still reach.
Price against remaining support
A simple way to compare is cost per remaining month of support. If a used speaker costs half the price of a new one but has a quarter of the support left, the new one is the better buy. If the maker does not publish an end date, estimate conservatively and assume the shortest plausible period. Then decide whether you would still buy at that price.
Write the support end date in your calendar the day you buy. When it arrives, you will know the device has become a risk and can plan its retirement rather than finding out from a news story.
Check the accessories too
Chargers, hubs and bridges that came with the device may carry their own firmware. Ask whether they are included, whether they are also supported, and reset them in the same way. A hub left with the previous owner's pairing can cause odd behavior that is hard to trace.
Warning signs
- The seller cannot say what model it is, or the label has been removed.
- The device is locked to another account that you cannot get cleared.
- The maker has ended support, or you cannot find out.
- The device behaves oddly after a reset, such as connecting to unknown services.
A simple rule
If the end of support is close, buy only if the price reflects that and you plan to retire the device when it arrives. Otherwise, buy new from a seller who states the support period.
Quick check
Is a factory reset enough to trust a used device?
It removes the previous owner's data and settings. It does not add support that the maker has ended, so check support too.
Sources
Last reviewed: 19 October 2026.
