Free · runs in your browser
If every video lags, the problem is your browser, app or headphones. If only your own upload does, fix the file before it goes up.
When YouTube audio is out of sync, check whether it happens on every video or only one. If every video lags, the cause is on your side: the browser, an extension, graphics acceleration, the app or Bluetooth headphones. If only one video is out of sync, on every device, the uploaded file itself was out of step, and only the person who uploaded it can fix it by uploading a corrected file.
This page covers both. For viewers, the steps below go from the quickest fix to the most thorough. For creators, YouTube’s own help says to make the audio and video tracks the same length and edit them before uploading; the tool above does that for the timing itself: open your video, press Detect automatically or line up a clap, nudge the sound Earlier or Later, and Export video with the picture untouched.
The first three steps are for watching; the last is for your own uploads.
Reload the page or restart the app, then play a different video. If that one is fine, the first video is the problem, not your setup.
In Chrome, turn Use graphics acceleration when available off (or on) under Settings → System and relaunch. Try a private window, which runs without most extensions, or Firefox’s Troubleshoot Mode.
Unplug or disconnect Bluetooth headphones and play through the device’s speakers. If the lag disappears, see Bluetooth audio delay.
Open the file above, press Detect automatically (A), check a clear word with Replay around here (L), adjust with Earlier or Later, then Export video and upload the new file.
One video out of sync everywhere, on your phone and your computer alike, was uploaded that way. Nothing on your side will fix it; a comment to the creator might. Every video out of sync on one device means that device is the cause.
On a TV, every app including YouTube may be off because of the TV’s picture processing or a soundbar: see the TV guide. With wireless headphones, YouTube usually compensates, but not on every device; measure with the audio delay test.
YouTube plays what you upload. If the file is out of sync on your own computer, it will be out of sync for every viewer, so fix it before it goes up.
YouTube’s help also says to make the sound and picture the same length. A file whose sound is much shorter or longer than its picture can be timed oddly after processing.
If every video is affected, the browser is struggling: try switching graphics acceleration, closing other tabs, a private window without extensions, and disconnecting Bluetooth headphones. If only one video is affected, it was uploaded out of sync.
Usually because the file was already out of sync, or its sound and picture had different lengths. Check the file before uploading, fix the timing here, and upload the corrected copy.
YouTube doesn’t let you replace the file of a published video. Fix your original, upload it as a new video and remove or unlist the old one.
On some computers, yes; on others it makes playback worse. Change the setting, relaunch the browser and compare.
The video is fine; the TV or its sound system adds delay. Game mode, PCM output and the TV’s audio sync setting usually fix it.