Bootloader

A bootloader is the first program that runs when you switch on a phone and checks the system is genuine; unlocking it weakens the phone's protection.

Bootloader: The bootloader is the small program that starts when you power on a phone. It loads the operating system, and on a locked phone it checks that the system software has not been changed. Unlocking it lets you install other software, but removes this safety check.

Most phones are sold with a locked bootloader. Hobbyists unlock it to install custom versions of Android. Once unlocked, anyone with the phone can load their own software, which could hide spyware in a way that normal apps cannot see. Banking apps and some payment apps may refuse to run on such phones. Some thieves unlock phones they steal, so a phone that was fine before can show this warning later.

When buying a second-hand phone, check that it has not been unlocked or modified. Many phones show a warning about an unlocked bootloader every time they start. Do not unlock yours unless you know exactly what you are doing and are prepared to lose protection and, on some brands, the warranty. Ask the seller to show the phone starting up so that you can see any warning.

Tips

• Avoid buying a used phone that shows an unlocked bootloader warning at start-up.
• Do not unlock your own bootloader just to try a custom ROM if you use banking apps.
• Keep your phone's official software and security updates in place.

Related terms