Something is wrong
Sound in one ear only
One side silent has four completely different causes, and three of them are free to fix. The trouble is that they all feel identical, so people replace headphones that were never broken. This settles it in about two minutes, cheapest cause first.
The run, in order
Push the plug all the way in, then try again
The single most common cause, and the one people skip because it seems too obvious. A 3.5 mm plug carries left, right and ground on separate rings along its length; one step short and a channel is simply not connected. Thick phone cases and recessed sockets cause this constantly.
Play the left and right channels separately
Confirms which side is actually silent, and rules out the case where both sides work but the audio is being mixed to mono. If a one-sided test plays on both sides, nothing is broken at all — a mono accessibility setting is on.
Centre the balance control
A system-wide slider that survives reboots and applies to everything. Windows: Settings, System, Sound, your output device, where left and right have separate sliders. macOS: System Settings, Sound, Output, balance slider. It is easy to move by accident and produces exactly this symptom.
Flex the cable near the plug while sound is playing
If the sound cuts in and out as you move it, the cable has broken there — which is where headphone cables nearly always fail, from the bending. This is the point at which the headphones really are the problem.
Try the same headphones on another device
The step that separates the headphones from the computer, and takes ten seconds. Silent on both means the headphones; fine on a phone means the computer or its socket.
If both sides now work but something still sounds wrong, check polarity
A different fault that gets mistaken for this one. Speakers wired in reverse both work, both play on the correct sides, and cancel each other in the middle — which people describe as sound coming from one side.
Why the order matters
Each step costs more than the one before it — first in effort, then in money. Three quarters of the cases that reach a page like this are solved by the first three steps, all of which are free and none of which involve deciding your headphones are broken.
Reading the outcome
| What you find | What it is |
|---|---|
| Fixed by pushing the plug in | The plug was not seated |
| One-sided test plays on both sides | Mono downmix setting |
| Fixed by centring balance | Balance offset |
| Cuts in and out when the cable moves | Broken cable at the plug |
| Silent on every device | Failed driver |
| Fine on a phone, silent on the computer | The socket or the sound settings |
The one that is not this fault at all
If both channels test correctly and the sound still seems to come from one side, or seems to have no middle, run the polarity test. Speakers or headphones wired in reverse pass every check on this page and still sound wrong, because the two sides cancel rather than one failing. It is a different problem with a different fix, and it is free.
Common questions
Both sides play when I test only one. What does that mean?
That the audio is being downmixed to mono before it reaches your headphones. On Windows this is Settings, Accessibility, Audio, Mono audio. On macOS it is System Settings, Accessibility, Audio, Play stereo audio as mono. Some Bluetooth headsets also collapse to mono whenever an application opens the microphone, which is why a headset can be stereo for music and mono on a call.
One side is quieter rather than silent.
Check the balance first, because it is a slider rather than a switch and a small offset is easy to make. If balance is centred, an unevenly worn driver or a partly broken cable core will do it, and both get worse over time rather than better.
It only happens on calls.
Then it is almost certainly the headset switching to hands-free mode, which most Bluetooth devices do when the microphone is opened. Quality drops sharply and some devices go mono in the process. It is the Bluetooth protocol rather than your headphones, and it happens on every device they connect to.
It works in one application but not another.
Applications keep their own output selection and often their own volume, separately from the system. Check the audio settings inside the application itself. This is also why a browser can be fine while a game is not.
Can a broken cable be repaired?
On headphones with a detachable cable, replacing it costs very little and is worth doing before anything else. On a fixed cable it is a soldering job near the plug, which is worth it only on expensive headphones.