I hear the left tone in both ears. Why?

A mono setting or sound enhancement may be mixing the channels. Check your system accessibility and sound settings. Phone speakers are often a single mono speaker.

I cannot hear the highest tones.

That is normal. The upper limit of hearing falls with age, and small speakers also roll off at both ends.

Is anything recorded or uploaded?

No. The test runs entirely in your browser. Nothing is recorded, stored or sent to a server.

Speaker and Headphone Test - Free Online Tool

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Play tones on the left and right channels and run a frequency sweep.