Headphone and earbud test
Check which ear plays, whether both are equally loud and how low your headphones go. Keep the volume low at first.
Press left, right or both to start. Space stops everything.
Sound
Phase
Left, right and balance
Press left: only the left ear should play, and it should match the L mark on your headphones. Do the same with right. Then press both with pink noise: the sound should seem to sit in the middle of your head, not leaning to one side. If it leans, one driver is weaker or the balance setting is off.
Low and high end
Use the sweep to hear the whole range from 20 Hz to 20 kHz. Small earbuds usually fade out below 60 Hz, and everybody hears the top end differently, especially with age. A buzz or rattle at one pitch can point to a loose part, a bad seal or a damaged driver.
Bluetooth and wired
Bluetooth earbuds can take a moment to wake up, so the first fraction of a second may be missing: press the button again. If the left and right sound identical on a phone, check that mono audio is off in the accessibility settings.
The oscilloscope shows the signal this page sends, not what comes out of the earbud, so use it to tell a clean signal from a faulty player or cable.
Questions
Left and right are swapped. How do I fix it?
Press Left. If the sound comes from the right side, the channels are reversed. Check the output settings of your system or audio interface, and how the speaker cables are connected.
With headphones, check that you are wearing them the right way round: the small L and R marks are easy to miss.
One speaker is quieter than the other.
Play Both and listen from the middle between the speakers. If one side is clearly quieter, check the balance slider in your system and in the app you use, then the cable.
Then swap the two speakers' places. If the quiet sound moves with the speaker, that speaker is weaker. If it stays on the same side of the room, the cause is the room or the setup, for example a speaker pushed into a corner.
Does it work on a phone or tablet?
Yes, in current browsers. Tap a button to start, because browsers only allow sound after a tap. If you hear nothing on an iPhone, check that the silent switch is off and the volume is up.
Many phone speakers are mono or only weakly stereo, so a left and right test makes more sense with headphones.
Can I test headphones and earbuds?
Yes. Press Left and check which ear plays; it should match the L mark on the headphones. Then check Right and Both. Keep the volume low.
Bluetooth earbuds can need a moment to wake up, so the first fraction of a second may be missed. Press the button again if you hear nothing.