Wi-Fi Sensing: How a Router Detects Movement in an Apartment and What It Means for Privacy

For most people, a Wi-Fi router is just a box that provides internet access. However, the radio signals it transmits also react to what’s happening in the room. A person walking through an apartment slightly alters those signals. A technology called Wi-Fi Sensing uses these changes to detect motion without a camera. It really does work, but claims that the router “sees through walls” and measures heart rate are greatly exaggerated.

How Wi-Fi Sensing Works

The router and devices in the home constantly communicate with each other via radio waves. These waves bounce off walls, furniture, and people, and the receiver can determine how the signal has changed along the way. This is called Channel State Information (CSI). If someone moves within the space, these values change over time, and the software can interpret this as movement or presence.

The principle is similar to radar, but it uses a signal that is already active in the apartment. It is therefore not an image of the room, but a statistical analysis of changes in the signal.

The 802.11bf Standard

The technology is not new and has been used in research and in some products for years. What is new is the standard: a revision of the Wi-Fi standard designated IEEE 802.11bf, which focuses on environmental monitoring (WLAN sensing). According to the IEEE 802.11 group’s schedule, it was published on September 26, 2025. It defines how devices exchange signals for sensing purposes and how measurement results are transmitted between them. It leaves it up to manufacturers to develop the specific algorithms that analyze the measurements to determine movement.

The standard itself, therefore, does not “enable” anything. It allows chips and devices from different manufacturers to support sensing in the same way and ensures that this capability is integrated into standard routers.

What Actually Works Today

Motion and Presence Detection

A proven and widely deployed feature is the ability to detect whether someone is moving inside an apartment. In August 2026, a major U.S. internet service provider made this feature available as part of a home security package on millions of compatible routers. According to the provider, the feature is disabled by default and must be enabled; it detects movement, but not the person’s identity or exact location within the home. According to a review study, when deployed on a large scale across more than 10 million routers, motion detection accuracy reached approximately 93%.

Breathing, Heart Rate, and Falls

Measuring breathing or heart rate and detecting falls via radio signals are the subject of research and prototyping. The sources we found describe these as potential capabilities of the technology, not as standard features of consumer routers. Similarly, we have not verified that a standard router can determine which room you are in or create a “3D model” of your home.

Practical Applications

• Home automation: lights or heating adjust based on the presence of people without you having to carry your phone.
• Security: Alerts about movement in the home when you’re away.
• Senior care: Detection of unusual inactivity or falls has long been discussed, though it remains primarily in the research phase.

Privacy Risks

Although the technology does not use a camera, data about when someone is home and when they are not is sensitive. Critics point out three problems.

Lack of rules at the standard level

According to analyses of the 802.11bf standard, it does not require the consent of individuals within the signal’s range or provide an opt-out option, and it leaves protection against eavesdropping on transmission signals up to manufacturers. These claims are based on secondary analyses, so please treat them as a cautionary note, not as a definitive legal conclusion.

No one asks a guest or neighbor for permission

The signal passes through walls, so theoretically it can track the movements of people who are unaware of the tracking and have never consented to it.

A Target for Attackers

Data on occupancy in an apartment may be of interest to attackers who want to know when the home is empty. There is also a risk that the feature could later be enabled by default or that the data could begin to be shared with other services.

Why VPNs and DNS Filters Won’t Help

Tools like VPNs or DNS filtering protect network traffic—that is, what you send and receive. However, traffic monitoring is based on the physical properties of the radio signal rather than the content of the communication, so these tools have no effect on it. What matters is who controls the router’s firmware and what they do with the measured data.

What You Can Do

• Check the router’s admin interface or app to see if there’s a feature labeled “motion detection” or “tracking.”
• If you don’t need it, leave it turned off and check again after firmware updates.
• If the feature is provided by your internet service provider, read up on where the data is sent and how long it is stored.
• Consider using your own router if you want to have control over its firmware.

Conclusion

Wi-Fi Sensing is a real technology that the 802.11bf standard is bringing from the lab to everyday devices. Today, it’s primarily about detecting motion and presence, not about monitoring heart rate or creating a 3D map of your home. However, privacy remains an open question: until there are clear rules regarding consent, data protection, and sharing, it’s wise to keep this feature turned off unless you really need it.