PIN, fingerprint, card, app or key: which to actually use

A lock that offers five ways in is not five times better than one that offers one. It is better because different people need different things from the same door, and because a single method with no fallback is a single point of failure.

The workhorse, and the reason smart locks took hold in short lets: a code can be issued before arrival, expire on checkout, and never needs collecting. For a home, give the window cleaner a code that works Tuesday mornings rather than a key that works forever.

The weakness is wear. A keypad used with the same four digits for a year shows which four they are. Locks that ask for random digits either side of the real code exist for exactly this reason — use that feature if the lock has it.

For the people who live there, this is the one that makes a smart lock feel worth having: no phone, no code, no pause. It struggles with wet hands, cold hands, and hands that do manual work — which is worth knowing before it becomes the only way anyone gets in. Enrol more than one finger per person, and enrol a second person.

Underrated, and often the answer when a keypad is the problem rather than the solution — an older relative who finds codes hard, a child who cannot reliably keep one secret, a cleaner who would rather carry something. A card is a physical token you can take back, without the copying problem a key has.

Useful for letting someone in when you are not there, and dependent on things outside the lock: your phone, your signal, and in most cases a bridge or gateway in the property. Convenient as an addition; a poor choice as your primary route in, because it has the most links in the chain.

Keep it. Not because the electronics are unreliable, but because it is the one method that needs nothing at all to work. Where the lock keeps a cylinder, someone who is not you should be able to get to a key.