Reviewed 19 September 2026Quick answer: use the same screen and output path that seem out of sync, lower the volume and run the 0 ms reference first. If every beep consistently feels early or late, adjust the sound offset and repeat. The selected value is a subjective comparison setting, not an automatic latency measurement.
Browser A/V sync referenceCompare a visual pulse with a short beep
Eight cues play at a slow interval. Start with the reference at 0 ms, then adjust only if the beep consistently feels early or late.
Negative values schedule the beep before the visual pulse; positive values schedule it after. The selected value is a comparison setting, not an automatic latency measurement.
Ready at the 0 ms reference. Lower the output volume before starting.
No microphone or recording. The small pulse repeats every 1.5 seconds and stops after eight cues.
How to run the audio sync test
- Connect the TV, soundbar, receiver, Bluetooth speaker or headphones you actually want to evaluate.
- Lower the output volume and keep headphones off your ears for the first cue.
- Leave the offset at Reference: 0 ms and start the eight-cue sequence.
- Watch the center of the visual pulse. Decide whether the beep consistently feels early, late or aligned across several cues.
- If needed, stop, move the offset in one direction and run the complete sequence again. Change only one device or setting between comparisons.
What the offset means
Sound feels late
Try a negative offset so the browser schedules the beep before the visual pulse. Use the value only as a comparison inside this page; a TV or receiver may label its correction direction differently.
Sound feels early
Try a positive offset so the beep is scheduled after the pulse. Confirm the direction with real speech or a familiar impact after changing the equipment setting.
The result changes between runs
Wireless buffering, browser load, display processing or the source app may vary. A changing result does not support one fixed correction value.
Everything looks aligned here
The original app, stream or input may have its own timing. Test the actual content and signal path before concluding that the system is synchronized everywhere.
Compare wired and Bluetooth audio delay
Run the reference once through a wired or built-in output, then repeat through the Bluetooth device without changing the screen or browser. This comparison can reveal that one route feels later. It cannot identify the active codec or separate browser, operating-system, radio, device-processing and display delay.
For channel routing before the sync comparison, use the speaker and sound test or headphone test. If the phone itself sounds muffled or delayed because of recent liquid rather than a timing mismatch, follow the wet-phone guide instead.
Why the browser cannot measure the whole path alone
The Web Audio specification describes cumulative latency from buffering, processing and output devices, and it notes that the audio timeline is not necessarily synchronized with other system clocks. The page therefore schedules a repeatable stimulus and asks the listener to compare it; it does not turn a slider choice into a hardware measurement.
Apple's Wireless Audio Sync procedure uses an iPhone near the TV or receiver speakers to measure the actual output path. That extra measurement device is why an operating-system calibration can do more than this no-permission browser reference.