Home Security Basics: What to Buy First

What should I buy first for home security?

A contact sensor. It is the cheapest device in the category and the only one that tells you a specific thing happened at a specific opening, with no camera to review and nothing to subscribe to. Most people start with a camera, which gives them a video feed they will not watch and a notification every time a cat crosses the garden. Sensors tell you facts; cameras give you footage to interpret.

The four layers, in buying order

1. Know when something opened — contact sensors

A contact sensor is two parts: a magnet on the moving leaf and a sensor on the frame. When they separate, it reports. That single fact covers the front door, the back door, the ground-floor windows, the garage side door and the patio slider, for a few dollars per opening. There is no footage to scrub through and no judgment call — the door was either open or it was not.

Buy these first for three reasons. They are the cheapest thing that changes anything. They need no plan, ever. And they are the layer that tells you where the gaps actually are: a week of sensor history teaches you which door the household really uses and which window nobody ever closes. The field is ranked in our door and window sensor roundup, and if you do not want a hub at all, in our no-hub sensor rankings.

2. Control the door — a smart lock

The second purchase is the lock, because the most common real failure in a house is not an intrusion: it is a door left unlocked. A smart lock with auto-lock closes that gap mechanically, and gives you codes instead of keys, which means the spare under the mat stops being part of the plan.

The decision here is retrofit or replacement. A retrofit motor sits over your existing thumbturn and needs no drilling, which is the only option in most rentals. A replacement deadbolt needs the right backset, cross-bore and door thickness — four minutes with a tape measure, worked through in will a smart lock fit my door. The whole field starts at our main smart lock roundup.

3. See the doorstep — a video doorbell

A doorbell is the first camera worth owning, because it points at the one place where something happens every day: parcels, visitors, people who knock and leave. It is also the camera with the clearest useful output — a short clip of somebody at your door is immediately legible in a way that a wide garden view is not.

The thing to check before buying is power. A wired doorbell needs a transformer and a chime circuit behind the existing button; a battery doorbell needs neither but needs charging and usually ships its own plug-in chime. Start at our doorbell rankings, and if you are not sure a doorbell is worth it at all, that question has its own page.

4. Cover the outside — one camera, deliberately placed

Last, and only one to begin with. Pick the single approach that matters — the drive, the side passage, the back gate — and put one camera on it with a narrow, deliberate job. A single camera that covers one thing properly is worth more than three covering everything badly, and it teaches you what you actually want from the next one.

Two questions decide the camera: where the footage is stored, and where the power comes from. Storage is the one with a bill attached, which is why this site ranks on it — see local storage versus cloud. Power decides whether you are running a cable, charging a battery, or relying on sun. Placement is its own skill, covered in where to place security cameras.

The two things most people get backwards

Buying the camera first.A camera is the most impressive device in the category and the least informative per dollar. It generates footage, which requires you to look at it, and alerts, which quickly become background noise. The sensor-first order exists because “the garage door has been open for forty minutes” is more useful than forty clips of a street.

Buying a system before buying a device. Alarm kits, hubs and base stations are usually not the first purchase. A single sensor and a single lock will tell you whether you want a hub at all, and what protocol it should speak. If you do end up wanting one, the decision is in our smart home hub guide, and the platform question — Apple Home, Google Home, Alexa, SmartThings or Home Assistant — in the ecosystem guide.

What a monthly plan does and does not buy

Almost every brand in this category sells a subscription, and almost none of them is required for the device to work at the door. What a plan typically adds is cloud video history and some cloud-side detection features. What it rarely adds is anything a sensor or a lock does. So the practical position is: you can build all four layers above with no recurring cost at all, and add a plan later if you decide you want off-site video retention.

The arithmetic matters because it compounds. A per-camera monthly fee on four cameras over five years is a larger number than the hardware cost, and we publish the comparison in what the plans actually cost. The hardware that works fully without one is collected at the no-subscription hub.

What you do not need

You do not need professional monitoring to use any of this; self-monitoring means the alerts come to your phone, and what that does and does not cover is a separate page. You do not need everything on one brand — mixing a lock from one maker with sensors from another is normal, and what makes it manageable is protocol rather than branding, explained in Matter explained. And you do not need to cover every opening on day one. Two sensors and a lock is a real improvement on nothing, and it costs less than one mid-range camera.