Click each button. A clean A4 (440 Hz) tone will play to one channel at a time. Headphones with reversed cabling will betray themselves immediately.
Generated client-side with Web Audio (OscillatorNode → StereoPannerNode → AudioDestinationNode). Output gain is held at -12 dBFS to avoid surprises. Sweep mode pans linearly L → R over 4 seconds.
A stereo test plays a known signal — here, a 440 Hz sine tone — to one channel at a time. It confirms three things: that both drivers physically work, that left and right are not swapped at the cable, plug, or driver level, and that the balance control in your OS is centred. Reversed channels are surprisingly common with cheap aux cables, USB DACs with miswired pinouts, and Bluetooth headsets where firmware bugs flip the stream. If 'Left only' plays in your right ear, you have a wiring or routing issue, not a hearing one.
A continuous tone that smoothly travels from your left ear, across the centre of your head, and out to your right ear over four seconds. There should be no dropouts, no sudden jumps to one side, and no volume dip in the middle (a centre dip suggests one driver is significantly quieter than the other or that you have a mono signal masquerading as stereo). If the sweep moves in the wrong direction, your channels are reversed.
That is normal on headphones — it is called in-head localisation and happens because both ears receive identical signals with no acoustic crosstalk or room cues. On speakers, the same signal should form a phantom centre image floating between the two boxes. If the phantom centre pulls hard to one side on speakers, check speaker placement symmetry, OS balance slider, and that you are sitting equidistant from both drivers.
Click any button first to start the AudioContext (browsers block audio until a user gesture). Then check: system volume above zero, correct output device selected in OS sound settings, browser tab not muted, and the tone is set to an audible frequency (try 440 Hz if you changed it). If only one side is silent, swap your headphones to the other socket or try a different cable before blaming the drivers. For a wider frequency check, use the sweep tool at https://devicecheckonline.com/audio/sweep.
Output is capped at -12 dBFS with the volume slider at default, which is comfortable on every consumer system we tested. Always start with your OS volume low and raise it gradually — a 440 Hz tone at full system volume on studio monitors or IEMs can be uncomfortable. Tweeters can be damaged by sustained high-frequency tones above 5 kHz at high SPL, so use the dedicated tone generator at https://devicecheckonline.com/audio/tone if you need extreme frequencies.
Yes, but with caveats. Many Bluetooth codecs (SBC, AAC) downsample or compress, so the tone may sound slightly warbled or delayed. Some headsets auto-switch to mono 'HFP/HSP' profile when a microphone is active — that collapses left and right into one channel, defeating the test. Disable any mic-using app, force A2DP stereo mode in your OS, and retry. For the cleanest test, use wired headphones plugged directly into the device.