Audio Delay Test: How Many Milliseconds Is Your Sound Behind?

How this audio delay test works

Every sound on this page is scheduled on your browser’s audio clock, so we know when each beep leaves the browser. What we cannot see is how long the rest of the chain takes: the operating system’s buffers, the connection to your headphones or TV, and whatever processing the device does before you hear anything. Each method below estimates that hidden part in a different way.

Sync slider. A square flashes once per second and a short beep plays with it. If your audio is late, the beep seems to trail the flash. Moving the slider delays the flash until both feel like a single event; the slider value is then your estimated audio delay. The screen can only change once per refresh, so a single reading carries an error of about half a frame (about 8 ms on a 60 Hz display) plus your own judgment of when two things are simultaneous, which for most people is in the tens of milliseconds. Locking in three times and using the median steadies the result.

Tap test. First you tap whenever the pad flashes, with no sound, which measures your reaction to light. Then you tap whenever you hear a beep, with no flash. The difference between the two medians is the estimated audio delay. It removes most of your reaction time, but not all of it: people usually react faster to sounds than to flashes, so this method tends to read lower than the true delay, and touchscreens add their own input delay. Treat it as a quick check rather than a precise figure.

Loop mode. The flash and beep repeat full screen so you can judge sync on a television or record the screen in slow motion. It does not compute a number by itself; for a number, use the slider or the frame calculator on the lip sync test.

Results are estimates of the whole playback chain – browser, system, connection and device – not the codec figure printed on a box. Different browsers and repeated runs will vary a little.

What your result means

A positive number means the sound reaches you after the picture; a negative number means it arrives first. Whether a given delay bothers you depends on what you are doing. For watching video, the most widely cited reference is Recommendation ITU-R BT.1359 from the International Telecommunication Union. In its subjective tests, viewers on average began to detect sound lagging the picture at about 125 ms and found it unacceptable at about 185 ms. For sound arriving early, the averages were about 45 ms to detect and about 90 ms to reject. This page uses those averages for the short verdict under your result:

These are averages from viewing tests, not hard limits, and your own perception is what counts. Games, music practice and video calls have no equivalent published threshold that we can point to, so we do not invent one: if a delay feels wrong while you play, it is worth reducing.

Which test should you use?

Comparing wired and wireless headphones? The Bluetooth latency test runs a beat test twice and subtracts the results, which cancels most of your own tapping habit.

Why sound lags behind the picture

Sound almost never travels straight from an app to your ears. It is handed from one stage to the next, and each stage keeps a little audio in reserve so it never runs dry. Those reserves are what you hear as delay.

Bluetooth encoding and buffering

Wireless headphones receive compressed audio over a radio link. The phone or computer encodes the sound, sends it in small packets, and the headphones decode it and hold some of it in a buffer so a missed packet does not cause a dropout. Larger buffers make the connection more robust but later. The codec in use, the headphones’ firmware and the quality of the radio link all change the size of that buffer, which is why two pairs of headphones on the same phone can measure quite differently.

TV picture processing

Televisions improve the picture by comparing several frames at once – for smoothing motion, reducing noise or upscaling. The picture is held back while that happens. If the sound goes straight to a soundbar or receiver, the picture can end up behind the sound; if the sound is processed too, the balance can swing the other way. Game modes cut most of that processing, which is why they often fix lip sync problems as a side effect.

Computer audio buffers

Operating systems and browsers mix sound from every app into one stream and send it to the hardware in blocks. A block must be complete before it plays, so bigger blocks mean more delay. Browsers choose comfortable sizes to avoid crackling, and some audio drivers add further buffering. Music software lets you shrink the buffer, but a browser generally decides for you.

How to reduce audio delay

Start with the cheapest fix: the one that removes a step from the chain. Measure again after each change so you know which one helped. Menu names below vary by brand and system version, so look for similar words if yours differ.

Windows

• Turn off sound enhancements and spatial sound for your output device in the sound settings.
• Use the device’s own driver rather than a generic one; for music software, an audio interface with a dedicated low-latency driver usually helps most.
• Close other apps that are playing or recording sound.

macOS

• Use wired headphones or the built-in speakers when timing matters.
• Check the sound output in System Settings and avoid routing audio through extra virtual devices.

Android

• Turn off sound effects or equaliser features you do not need.
• If your headphones have a companion app, look for a game or low-latency mode; the name varies by brand.

iPhone and iPad

• Turn off spatial audio or head tracking for the headphones if you do not need it.
• Use the headphones’ app, if it has one, to check for a low-latency or game setting.
• For games and music apps, wired headphones through an adapter avoid wireless delay entirely.

TV, soundbar and receiver

• Switch the TV to game mode, which usually cuts picture processing and therefore the picture delay.
• Look for an AV sync, audio delay or lip sync setting and use the number you measured here.
• Set the correction in one device only, ideally the last one in the chain, so two corrections do not fight each other.

Your privacy

The tests on this page never touch your microphone. They play beeps and show flashes, and every calculation happens in your browser. Nothing is uploaded and there is nothing to sign up for. We only count anonymous events such as “a test finished with a result between 100 and 200 ms”, never the exact number.

Details are in the privacy policy.