Magnetic Field Sweep
Measure changes in your phone’s magnetic sensor readings, keep a local reference and record locations to inspect. A field change cannot identify a hidden camera or tracker.
Sensor access depends on browser, hardware and permissions; the device report checks API presence. Every reading stays in this tab. Shortcuts: B sets the baseline, M marks a spot.
Start the sweep, then set a baseline away from metal.
Anomalies 0
Marked spots 0
A reading is not a device finding
A low reading does not rule out a magnet, camera or tracker on the path you moved. A plastic camera with no magnet, or one deep in a wall, will not show. Pair this sweep with the lens finder for optics.
How the magnetic sweep works
Readings come from your device's magnetometer through the W3C Generic Sensor API, sampled at up to 10 Hz. The page keeps about 30 minutes of readings in this tab.
- Baseline in the middle of the room, arm out, away from walls and metal. The page takes the median over 2.5 seconds and measures the spread as the noise floor. The Earth's field is about 25 to 65 µT and your phone adds its own offset, so only the deviation means anything.
- Sweep slowly at a consistent distance and orientation. Distance and movement change the signal; no fixed detection range is established here.
- Mark each place you check (M). The mark records the peak deviation over the last 2 seconds, so it catches the hit you just passed. Add a note and a verdict.
Browser support. The Magnetometer sensor needs a Chromium browser on Android over HTTPS; some builds need chrome://flags/#enable-generic-sensor-extra-classes switched on. When it is missing, the page offers a weaker compass mode from deviceorientationabsolute, which watches absolute orientation α in degrees, not field strength: hold the phone flat and slide it without turning. Exports are written by your browser.
How to read the result
- Deviation is the change from your captured reference. Colour thresholds are application heuristics, not calibrated uncertainty or device detection confidence.
- Threshold: 15 µT is the default; this is not a validated sensitivity limit. Auto uses four times the standard deviation measured during your baseline capture, with a floor of 5 µT.
- Shape in the anomaly table: under 1.5 s is a narrow spike; over 4 s is a broad rise; between is intermediate duration. These are timing labels, not source classifications. Movement speed changes duration.
- Reference quality: capture while still and repeat away from nearby objects if the readings vary. A baseline is a local reference, not instrument calibration.
Magnetic field detector FAQ
How can a magnetometer find a hidden camera?
A supported magnetometer reports local field readings. This page compares them with a reference you capture. Magnets, metal and other sources can affect readings, but a field change does not identify a hidden camera. Range and sensitivity have not been validated for your device.
Does the magnetic sweep work on iPhone?
Check the device report: API presence, permissions and actual readings determine whether this browser can measure. Missing API access does not prove the device lacks a physical sensor. A supported orientation fallback reports degrees, and the demo uses simulated data.
What alert threshold should I use?
15 µT is an application default, not a validated detection threshold. Auto uses four times the spread of your local reference, with a floor of 5 µT (4 degrees in compass mode). Adjusting it changes which readings trigger an excursion; it cannot establish a device finding.
What is the difference between a spike and a broad rise?
These are duration labels: under 1.5 seconds, over 4 seconds, and intermediate. Sweep speed and pauses affect the shape. Duration alone does not identify a magnet, material or device.
What else sets the detector off?
Steel studs, rebar, wiring under load, radiators, door frames, screws, curtain rails, laptop and tablet magnets, speakers, phone mounts and fridge doors. It misses a plastic camera with no magnet or one deep in a wall, so pair it with the lens finder.
Magnetic field units follow the W3C Magnetometer API. The compass fallback uses absolute orientation α, not field strength. A local reference is not instrument calibration. Thresholds are application heuristics; device sensitivity and detection range have not been validated.