Compass accuracy and device testing
Last updated October 7, 2026
A compass can display a whole degree without being accurate to one degree. Online Compass reads the heading your browser exposes; sensor quality, phone position and nearby magnetic fields still affect the result.
What is verified, and what is not
Software regression checks exercise magnetic sensor events, location-based declination, invalid readings, manual input and the absence of a sensor. A desktop browser check verifies that manual exploration is labelled and does not initially display a measured heading. Synthetic sensor events verify software behavior, not a physical magnetometer.
No measured iPhone or Android accuracy results are published here yet. A browser-emulated mobile screen is not a real phone test. We do not claim a tested device list or a numerical accuracy rating without a recorded comparison.
Browser requirements, not a tested-device guarantee
| Environment | Required capability | What to expect |
|---|---|---|
| iPhone or iPad with Safari | Usable webkitCompassHeading and motion permission | Magnetic heading; location is needed for a true-north correction. |
| Android browser | Absolute device-orientation events and compatible sensor hardware | Magnetic heading derived with the device held flat; location enables declination correction. |
| Desktop, missing sensor, or blocked sensor | No usable heading received | Manual exploration. Dragging the dial chooses a value; it does not find north. |
Use HTTPS, enable JavaScript and open the site directly in your browser rather than inside a social app. The tool does not request location until you choose a location-based feature. Permission prompts and settings vary by browser version.
What the north setting means
Before a location is available, supported sensor readings use magnetic north. True north requests your location and uses the World Magnetic Model to estimate declination locally. True bearing equals magnetic bearing plus signed declination, wrapped into 0–360°. A negative declination is subtracted.
WebKit supplies a magnetic compass heading. The native Compass app’s settings do not establish the reference of a website’s sensor event. The current mode is shown above the controls. With denied location access, the tool retains magnetic north.
If the compass does not start
- Open the compass and tap Start compass. Accept motion/orientation permission if prompted.
- If permission was denied, check your browser’s site permissions, then reload and try again. Opening directly in Safari or Chrome can avoid restrictions imposed by an in-app browser.
- If no usable reading arrives, the tool switches to manual exploration. The website cannot determine whether the hardware is missing, the browser blocks it, or the sensor is temporarily unavailable.
- If location is denied, you can still use magnetic readings where a sensor works. Location alone cannot determine which way a stationary phone faces.
A repeatable physical-device comparison
- Record the phone model, operating-system version, browser version, date and active north reference.
- Choose an open spot away from vehicles, steel furniture, speakers and electrical equipment. Remove a magnetic case.
- Place a reference compass and phone on a nonmagnetic surface, separated enough that they do not interfere. Compare magnetic north with magnetic north; otherwise record and apply the same declination.
- Hold the phone flat, align its top edge with a marked line, and let the reading settle. Record five readings for each of north, east, south and west, returning to the marked line each time.
- Report the individual readings, the spread and the shortest angular difference from the reference. For example, 359° versus 1° is a 2° difference, not 358°.
- Repeat after changing location or removing a case. Record failures as well as successful readings. A reference phone app may share the same sensor, so agreement with it alone is not independent proof.
You can send observations to [email protected]. Include the reference instrument and method; do not include a private address or exact coordinates unless you want to share them.
Privacy while testing
Heading and precise coordinates remain in the compass’s browser calculations. Page delivery, Google Analytics, AdSense and Cloudflare analytics are separate network activity. See the privacy policy; local sensor processing is not a claim that no website data is transmitted.
Technical references
- MDN: device orientation, permissions and compatibility
- WebKit: magnetic heading supplied to iOS orientation events
- NOAA: World Magnetic Model
Open the compass · Understand magnetic and true north · About the publisher