How accurate is an online pitch or vocal range test?
It depends on the method. A good browser test measures pitch dozens of times a second and only counts notes you hold steadily, so a crack or a slide doesn't count as your range.
Ours reads notes from E2–C6. Above C6 browser microphones stop being reliable (the very top of a soprano range), so we report C6 as “C6 or higher”. The pitch engine's octave errors on real singing were 0.16% of frames.
More questions: Is there an app that checks if I'm singing in tune? · What is a cent in singing? · Can you learn to sing in tune? · How do I find my vocal range? · How do I sing high notes without straining?