Door Sensor vs Motion Detection — What’s the Difference?

If you're trying to monitor activity at your door, you’ll usually come across two options: door sensors and motion detection alerts. While they sound similar, they work very differently.

What Is a Door Sensor?

A door sensor detects when a door is opened or closed. It typically uses a small magnet and sensor placed on the door and frame.

• Triggers when the door opens
• Common in alarm systems
• Does not detect activity before the door is opened

What Is Motion Detection?

Motion detection alerts you when movement is detected near your door — before the door is opened.

• Triggers when someone approaches your door
• Works for deliveries, visitors, or unexpected activity
• Gives you a heads-up before anything happens

Key Difference

The main difference is timing:

• Door sensor: alerts after the door opens
• Motion detection: alerts before the door opens

If you want to know when someone is already inside, a door sensor works. If you want to know when someone is approaching, motion detection is the better choice.

Which One Is Better for Deliveries?

For deliveries, motion detection is usually more useful. It lets you know someone is at your door even if they don’t knock or ring a bell.

A simple motion-based alert gives you awareness without requiring cameras, accounts, or interaction.

Simple Is Often Better

Many systems add complexity with apps, video feeds, or required actions. A simple alert can often give you exactly what you need — just awareness.