Stereo test
Press Left, Right or Both and check that each tone comes from the correct side and the centre sits between them.
Stereo test workspace
How to use
3 short steps.
Press Left
The tone should come only from the left speaker or left ear. Press it again to stop.
Press Right, then Both
Right should play only on the right. Both should sound like it comes from the middle.
Pan left to right
The tone moves smoothly from the left speaker to the right over three seconds without a gap in the middle.
What the result means
Match what you see to one of these.
Left is left and right is right
If each tone plays on its labelled side and Both sits in the centre, your stereo channels are wired correctly and the browser is sending true stereo.
The channels are swapped
If Left plays on the right, swap the speaker connections at the amplifier or computer, not the speakers. Red or marked plugs are the right channel by convention. Then replay Left.
The centre leans to one side or the pan jumps
If Both is off centre or the pan has a hole in the middle, centre the balance control and reseat the cables. Check that both speakers are the same distance from you.
Troubleshooting
If the test fails, try these in order.
Centre the balance
Reset the left-right balance in system sound settings, the player and any receiver, then replay Both.
Turn off spatial or surround processing
Disable virtual surround, Dolby Atmos for headphones and similar effects while you check basic stereo. Replay Left and Right.
Swap one connection at a time
Swap the left and right plugs at the amplifier or computer and press Left. If the sound moves to the correct side, the wiring was reversed; leave it swapped.
Try another source
Play a stereo video in another app. If it is also reversed, the problem is the connection, not this page. Retest here after each change.
What this test can't tell you
Where a browser check stops.
- Where the centre appears depends on speaker placement, headphone fit and the room, not only on the wiring.
- The browser cannot see how the speakers are wired; it can only play a tone on one channel and let you listen.
FAQ
Common questions about this test.
What is a stereo test?
A stereo test plays a sound on the left channel only, then the right, then both. It shows whether each speaker or earphone is connected to the correct channel and whether the two sides are balanced.
How do I check if my audio is stereo?
Press Left and then Right. If the tone is clearly on one side and then the other, the output is stereo. If both play the same on each side, the system is set to mono or the source is mono.
What do I do if the left and right channels are reversed?
Swap the two speaker connections at the amplifier or computer, or turn headphones the right way round. Check that the red or marked plug is the right channel, then press Left again.
What does the Both button do?
It sends the same tone to both channels at once. With two equal speakers the sound appears in the middle; if it leans, one side is quieter or the balance is off.