Check left/right channels and frequency response — no permissions needed
Wear your headphones, or sit between your speakers. Play one channel at a time.
Alternates left ↔ right three times — you should hear it clearly switch ears.
A rising tone across the human hearing range. Lower the volume first.
This page generates tones directly in your browser with the Web Audio API — no audio files, no permissions, no uploads. The channel test routes a short ping to only the left or only the right output, which is the fastest way to confirm both speakers (or both headphone drivers) are wired correctly and that your OS hasn't swapped channels.
The frequency sweep plays a continuous tone from 20 Hz to 20 kHz. You are not meant to hear all of it: sensitivity drops sharply above ~15 kHz and most adults hear nothing above 16–18 kHz, so a silent top end is normal — it usually describes your ears, not your speakers.
First check the obvious: headphone plug fully inserted, mono/stereo balance slider in the OS not panned hard to one side (Windows: Sound settings → speaker properties → balance; macOS: System Settings → Sound → balance), and the correct output device selected. Bluetooth headphones in mono mode, or a partially broken cable, are the most common causes of one-sided audio.
If both channels are silent but the meter elsewhere in the OS moves, the browser may be muted — check the tab's speaker icon and the per-app volume mixer. Trying a different output device (built-in speakers vs headphones) quickly narrows it to hardware vs settings.