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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteA Raspberry Pi can scan your home network for active devices and help you check whether a phone or laptop you recognize is connected. The project behind this headline is a local Wi-Fi presence detector—not a way to uncover every device tracking your family. It scans visible IPv4 devices on the network and compares their MAC addresses with addresses you already know.
What the Raspberry Pi project actually detects
The Raspberry Pi Official Magazine project, “Wifi detector – know who’s at home”, uses the command-line utility arp-scan to find active IPv4 devices visible on the local network. The example checks scan results for known devices, such as a family member’s phone or laptop, to infer whether those devices are connected.
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That is a limited, time-specific network inventory. It does not detect every tracker, spyware, web tracking, or all wireless devices nearby. Results depend on the network layout, device state, and what the scanner can see; a scan cannot establish that every household device has been found.
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How the scan works
The legacy tutorial describes installing arp-scan and running sudo arp-scan -l to list active IPv4 devices on the local network. You can compare an address in the output with a known device address; a script can repeat that check for several known devices.
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The article is an older tutorial and does not establish that its commands and dependencies have been validated on a current Raspberry Pi OS release. Treat it as an outline of the method, not a verified build guide for every current Pi.
Why a MAC address may not identify a device permanently
A MAC address in scan output is not necessarily a permanent identifier for a physical phone or laptop. Apple devices can use per-network private Wi-Fi addresses in fixed or rotating modes. Apple explains: “A rotating private address reduces tracking by periodically changing this device’s Wi-Fi address on the network.” The explanation appears in “Wi-Fi privacy with Apple devices,” published December 19, 2024.
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Android 10 and later use randomized MAC addresses by default for Wi-Fi connections; whether an address persists or changes depends on conditions. The Android Open Source Project documents this behavior in “MAC randomization behavior”. As a result, an address may be associated with a device’s connection to a network without serving as a stable identifier across time or networks.
Check your Raspberry Pi’s Wi-Fi hardware
Wireless capability varies by Raspberry Pi model. A Pi without built-in Wi-Fi can use a USB Wi-Fi adapter, but not every adapter or model supports 5 GHz. Raspberry Pi’s getting-started documentation describes these hardware caveats. Check the documentation for your specific Pi and adapter before choosing this approach; the project article does not specify a current model or establish compatibility with a particular OS release.
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Choose a method that matches the job
| Approach | Best suited to | What it depends on | What it does not establish |
|---|---|---|---|
Raspberry Pi with arp-scan |
Checking whether known devices are visible on the local network at scan time | A compatible Pi and network access; matching results to device addresses that may change | Every device in the home, nearby wireless devices, or tracking and spyware detection |
| Home Assistant device trackers | Household presence workflows, including zones and automations | A supported tracker integration or app, configured in Home Assistant | A feature of the old Raspberry Pi script or guaranteed detection of every device |
| Pi-hole | DNS filtering | DNS traffic routed through its filtering service | A replacement for scanning the local network to inventory devices |
Home Assistant documents tracker entities and presence workflows in its device tracker documentation and presence detection guide. These provide a path toward automations, rather than just a scan result. Pi-hole describes its scope as DNS filtering in its overview; it is not a device-discovery tool.
Quick Recap
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