Open compass.fyi on a smartphone with a compass. Hold the phone level and it should show your direction.
Is this accurate?
No, not really. Results may vary. As of this writing, Firefox and Chrome browsers handle the DeviceOrientation spec differently. It's only been tested on Chrome for Android.
- When the screen is rotated, the image gets rotated 90 degrees. I don't know how this could be fixed.
The images used in this app were labeled for reuse with modification: