Check left and right audio
Play a short tone on the left, right or both sides. Alternate between channels to check your headphone or speaker routing.
Start at low device volume. Stop if the sound is uncomfortable. Do not turn up quiet or inaudible tones.
Ready
Audio off
Audio is generated locally with Web Audio. Use your system sound settings to select the output device.
Use this left right audio test when a stereo recording seems backwards, a headset has no clear markings or a speaker cable may be connected to the wrong output. The large buttons play a short tone on the named channel. Left should reach your left side, Right should reach your right side, and Both should reach both. The label on screen shows which signal the browser is currently sending.
Start at low device volume and choose Left first. Check the physical position of the headphones or speakers rather than relying on a familiar song, since music can contain instruments panned in unexpected directions. Choose Right next and compare. Both is useful for confirming that each side works at the same time. Alternate switches sides through eight short bursts so you can follow the routing without repeatedly pressing buttons.
If the sides are reversed, look for an orientation or connection issue. Headphone cups may be worn backwards, separate speaker leads may be swapped, or an audio interface may route its outputs differently from the usual stereo pair. Change one setting at a time and repeat the same short test. Wireless devices can also expose more than one playback mode, so check which output your operating system has selected.
Hearing a left-only tone from both sides does not automatically mean the tool or device is broken. A mono accessibility setting deliberately combines stereo channels. Spatial processing, virtual surround and some headphone effects can also spread a signal across both sides. Temporarily disable those features for a direct channel check. With speakers, sound from the left speaker naturally reaches both sides of the room, so identify the physical source instead.
These checks confirm audible channel routing, not the quality of a recording or the accuracy of a speaker system. There is no microphone input and no automatic diagnosis. The browser creates the tone on your device without uploading audio. Stop audio or press Escape whenever you want to end playback. For a broader check, follow the headphone or speaker test below; for a sustained signal at a chosen frequency, open the tone generator. The mic test checks the input side of your setup.
FAQ
How do I know if my channels are swapped? +
Press Left and confirm that the tone comes from your left headphone cup or speaker. Repeat with Right. If both play on the opposite side, check headphone orientation, cables and output routing.
Why do I hear both sides during a left-only test? +
Mono audio, a spatial audio effect, a speaker crossfeed feature or an adapter can combine channels. Disable those settings temporarily and repeat the check with a known stereo output.
Why is there no sound? +
Confirm that the browser tab and system output are not muted, select the intended output in system settings, and press a channel button again. Bluetooth connections may take a moment to become ready.
Does Alternate keep playing forever? +
No. Alternate plays eight short bursts, switching between left and right, and then stops. You can stop sooner with the Stop audio button or Escape.
Do I need to upload a test track? +
No. The tone is generated locally by your browser. You do not need a file, microphone permission or an account.