Run the check
Play the left and right channel prompts at a safe volume. Note whether one side is silent or whether the labels are merely reversed.
Check system balance and mono-audio settings, then replay the same prompts without changing the source file.
Reseat a wired plug or re-pair both wireless earbuds, then compare the headphones on another device.
Read the result
A silent side across sources and devices is different from reversed channels or a single app's balance setting. If another headset works through the same port, the original headset needs inspection.
Limits and next step
The browser generates channel prompts but cannot measure sound at your ears or inspect earbud charge contacts.
Repeat the check after changing one setting or connection. Keep a record of what changed before deciding whether the device needs service.