This audio latency test measures how late your sound arrives, in milliseconds, for built-in speakers, wired and Bluetooth headphones, USB headsets, soundbars and TVs. The sync test plays a click while a lamp flashes, and you shift the picture until both happen together, which gives the delay you actually experience. The mic loopback plays a short chirp and listens for it seven times, for a round trip figure with its spread. The page also shows what your browser reports about its own audio delay, and keeps results so you can compare wired with wireless. Use it as an audio delay test for any output, in Chrome, Edge, Firefox and Safari on Windows, Mac, ChromeOS, Android and iPhone.
How to run the sync test
- Connect the headphones or speakers you want to test and make them your sound output. In Chrome and Edge you can also pick them in Output.
- Press Start sync test. A click plays every 1.2 seconds as the lamp flashes and the marker hits the centre line.
- Drag the slider until the click lands exactly when the marker hits the line. Use -1 and +1, or the arrow keys, for the last few milliseconds.
- Stop when they match. The number is how many milliseconds your sound arrives after the picture.
- Choose what you measured, such as Bluetooth, and press Save result. Repeat with wired headphones or speakers to see the difference.
Judge from the click, not the lamp alone. Most people line up sound and motion most precisely by watching the marker cross the line. Repeat the test two or three times and use the middle value.
How to run the mic loopback
- Choose Mic loopback and place the mic close to the speaker. For headphones, hold an earcup or earbud right against the mic.
- Press Start loopback and allow the microphone. Keep the room quiet for about five seconds.
- Read the seven runs, the median in Your result and the Spread. The waveform shows where the click was sent and where the mic heard it.
The loopback turns off echo cancellation, which would otherwise erase the click from the mic signal. If the clicks are not heard, raise Click volume or your system volume.
What the numbers mean
| Reading | What it tells you | Typical values |
|---|---|---|
| Your result, sync test | How much later you hear a sound than you see it on this screen | A few tens of ms wired, often well over 100 ms on Bluetooth |
| Your result, loopback | Round trip: output, air and mic input together | Higher than the sync test for the same output |
| Spread | The gap between the fastest and slowest loopback run | Small for wired, larger for Bluetooth |
| Browser output latency | The browser's estimate of the delay after it hands sound to the system | Often less than the real Bluetooth delay |
| Browser base latency | The browser's own audio buffer | A few ms |
How much delay people notice
Standards for television give useful limits. The ITU found that viewers start to notice when sound comes more than 125 ms after the picture, or more than 45 ms before it (ITU-R BT.1359). The European Broadcasting Union asks broadcasters to keep sound within 60 ms after and 40 ms before the picture (EBU R37), and the US ATSC sets a tighter 45 ms after and 15 ms before. Games are less forgiving because there is no video player to correct the delay, and players feel it on every shot and footstep.
Bluetooth codecs and their delay
The codec is the format the phone or computer uses to send sound to your headphones. Both sides must support it, and the delay you measure also depends on how much the headphones buffer, which is why a Bluetooth audio latency test on your own pair beats any table.
| Codec | Delay | Where you find it |
|---|---|---|
| SBC | Often 150 to 300 ms, depending mostly on the headphones | Every Bluetooth headphone, the fallback |
| AAC | In the same range as SBC, and sometimes higher on Android | iPhone, iPad, Mac and many Android phones |
| aptX | In the same range as SBC in independent tests | Many Android phones and some PCs |
| aptX Adaptive | About 80 ms in its low delay mode, according to Qualcomm | Recent Android phones with Snapdragon chips |
| aptX Low Latency | About 40 ms, according to Qualcomm | Older transmitters and headphones built for TV and games |
| LC3 with LE Audio | Built for low delay, with 7.5 ms or 10 ms audio frames | Newer phones, PCs and earbuds that support LE Audio |
On Android you can see the codec in use under Settings, then System, then Developer options, then Bluetooth audio codec. iPhones use AAC with most headphones.
Sound from Bluetooth headphones lags behind the picture
- Use the app's sync setting. In VLC, open Tools, then Track Synchronization, and set Audio track synchronization to a negative value equal to your result, for example -0.200 s. Many games and rhythm games have an audio offset setting too.
- Turn on the headphones' low delay mode. Many earbuds have a game or low latency mode in their companion app. It trades some sound quality or battery for delay.
- Pick a faster codec. On Android, choose aptX Adaptive in Developer options when the phone and headphones both support it. Plain aptX is mainly about sound quality and is not much faster than SBC.
- Keep the source close. Weak signals make some headphones buffer more. Keep the phone or computer in the same room, with nothing between it and the headphones.
- Go wired or use a dongle for gaming. Wired headphones add almost no delay, and gaming headsets with their own USB wireless dongle are far faster than Bluetooth.
If the headphones drop out or will not connect, start with the fixes for bluetooth not working, or for airpods not connecting. The bluetooth test checks your adapter.
Sound and picture out of sync on a TV
Connect a laptop to the TV with HDMI, show this page on the TV and run the sync test using the TV speakers or soundbar. The result is the TV's own lip sync error.
- Sound ahead of the picture is common with soundbars on optical or HDMI ARC, because the TV spends longer processing video. Delay the sound with the TV or soundbar setting: LG calls it Match Screen and Sound (AV Sync Adjustment on models from before 2021), Sony calls it A/V sync, and Samsung offers Digital Output Audio Delay in its Expert Settings for optical and HDMI ARC output.
- Sound behind the picture usually comes from Bluetooth headphones or speakers on the TV. Some TVs can hold back the picture to match, such as Sony with the A/V sync option in its Bluetooth device settings, but many cannot; Samsung says none of its settings fix Bluetooth delay. If your TV cannot, use wired headphones, or a TV transmitter and headphones that both support aptX Low Latency. With wireless speakers on an Apple TV, go to Settings, then Video and Audio, then Calibration, then Wireless Audio Sync, which measures the delay with an iPhone.
What an audio latency test cannot do
The sync test relies on your eyes and ears, and it measures sound against your screen, so a slow screen lowers the result slightly. The input lag test covers the screen side. The loopback adds the mic's own delay and needs echo cancellation off, which a few browsers ignore. No website can read which Bluetooth codec is in use, and what the browser reports often leaves out the headphones' buffer. Your own reaction speed does not affect either method, but if you want to measure it, try the reaction time test. To check that both sides of your headphones play evenly, use the headphone test.
Audio latency test questions
What is a good audio latency?
For games, as low as you can get, because nothing corrects the delay; wired headphones are the safe choice. For video, broadcasters aim to keep sound no more than 60 ms behind the picture, and most viewers only notice once sound lags by about 125 ms. Typical Bluetooth headphones sit above that, so they rely on the video app to correct the delay.
How do I test Bluetooth audio delay?
Connect the headphones and make them your output. Press Start sync test, then move the slider until the click lands exactly when the flash lights. Save it as Bluetooth, then repeat with wired headphones or the built-in speakers and save that too. The difference is what Bluetooth adds.
Why are Bluetooth headphones out of sync with video?
Bluetooth compresses sound into packets and the headphones keep a buffer of them to avoid dropouts, which adds delay. Most video apps delay the picture to match when the system reports the headphone delay correctly. When it does not, as with some browsers, games and older devices, speech lands visibly after the lips move.
Does a newer Bluetooth version have less delay?
Not by itself. The codec and the way the headphones buffer sound matter far more than the version number. LE Audio, added in Bluetooth 5.2 with the LC3 codec, was designed for lower delay, but only helps when the phone or computer and the earbuds both support it.
What do output latency and base latency mean?
Base latency is the time your browser's audio engine takes to hand sound to the system. Output latency is the browser's estimate of the time from there until the device plays it. Many browsers do not know the full Bluetooth delay, so these often read lower than the sync test.
Why is the loopback result higher than the sync test?
The loopback measures a full round trip: out through the speaker, through the air and back in through the mic, including the mic's own buffer. The sync test measures sound against the picture on your screen. Both are right for what they measure, and comparing two outputs with the same method is what matters.