How to compare sensor readings after a reboot

A compass heading changes, the motion readings look different, or a sensor stops appearing after you restart your device. A reboot can reset a browser session or a system service, but small changes can also come from how you hold the device or what is around it.

Use the same test before and after restarting so you can tell a real change from a different setup. The Sensors Test checks the sensors your browser can access, including motion, gyroscope, compass, light, location, and vibration.

Compare readings before and after reboot

1. Open the Sensors Test on the device you want to check. Allow any permission the browser requests, and note which sensor readings or tests are available.
2. Before rebooting, place the device in a stable position. Write down the readings you can see, along with the device orientation, location, and room conditions. For motion readings, leave the device still for several seconds, then repeat the same movement each time.
3. Restart the device normally. After it starts, reopen the same browser and test page. Keep the device in the same position and wait about the same amount of time before noting the readings.
4. Compare each sensor separately. For location, test in the same place. For the compass, keep away from metal objects and speakers. For light, keep the screen and sensor exposed to the same lighting.

Record the time and any changes you made, such as reconnecting a case or moving to another room. A short note is often more useful than trying to remember values from before the reboot.

What the changed readings mean

Motion or gyroscope values shift while the device is still

Small movements can change motion readings, and the axes may depend on how the device is turned. When a device is resting flat, an accelerometer can still show gravity, around 9.8 meters per second squared across its axes. A gyroscope usually reads close to zero when the device is not rotating. Compare the same orientation and look for a repeated difference, not a single changing digit.

The compass points in a different direction

Compass readings can drift or jump near metal, magnets, speakers, and some cases. The device may also need calibration. Move to an open area and repeat the test with the same orientation. A difference of a few degrees can be normal, while a heading that remains far off in several locations is worth checking further.

Light readings change

The light sensor measures the light reaching its sensor, not the brightness setting on your screen. A hand, case, window, or even a small change in angle can affect the reading. Keep the sensor uncovered and compare in steady lighting before treating a change as a fault.

Location changes or takes longer to appear

Location is provided through the browser and device location services. It is not always a direct reading from a single sensor. Indoor location can be less accurate, and a fresh reading after reboot may take longer or show a different accuracy estimate. Compare outdoors or near the same window, and check that the browser still has location permission.

A sensor or vibration test is missing

The browser may not support that sensor, the device may not have it, or access may be blocked. Vibration is an action rather than a numeric reading, so compare whether the same test response happens before and after. A missing result by itself does not prove that hardware is broken.

Fix a sensor that changed after reboot

1. Check the browser's site permissions. Open the site controls beside the address bar and review any permission for location or motion sensors. Allow access if you denied it, then reload the test. Permission names and availability vary by browser.
2. Check location access in the operating system. On Windows 11, open Settings › Privacy & security › Location. On macOS, open System Settings › Privacy & Security › Location Services. On Android, check Settings › Location. On iPhone, check Settings › Privacy & Security › Location Services. Also make sure the browser is allowed to use location where it appears in the list.
3. Repeat the comparison in a steady setup. Remove anything covering the sensor, set the device down, and use the same room and orientation. Close apps that use location or motion data, then reload the test.
4. Recalibrate the compass if needed. Follow the device maker's calibration instructions, then test away from metal furniture, magnetic cases, and speakers. Do not assume a compass issue explains changes in motion or light readings.
5. Restart the browser and check for updates. Close the browser completely, reopen it, and install available browser or operating system updates. If the issue began after an update, note the version and test again after a normal restart.

When it may be a hardware problem

A browser test cannot inspect every sensor or confirm that a component is physically damaged. If one sensor repeatedly gives implausible readings in the same conditions, check it in another app that uses that sensor. If the same problem appears there too, especially after a drop or liquid exposure, contact the device maker or a repair shop. For a new device, use the warranty before paying for a repair.

Why a browser test can show different sensors

Browsers expose only the sensor data that the device, operating system, and browser make available. A laptop may not have a compass or motion sensor, while a phone may restrict access until you grant permission. The Sensors Test must run on the device being checked, because another computer or phone cannot report its physical sensors for you.

Sensor readings and recordings from this test stay on your device. Location access is used by the browser to provide a location result, so allow it only when you want to check that sensor.