How do I know whether to use a positive or negative number?

Watch a moment with a clear sound and picture cue — a clap, a door, a spoken word. If you hear it before you see it, the audio is early: use a positive value to delay it. If you hear it after you see it, use a negative value to bring it forward.

How many milliseconds should I use?

Most sync problems are between 100 and 500 ms. Start with 200, check the result, and refine — a lip-sync error under about 40 ms is not noticeable.

Does this re-encode the video?

No. The video stream is copied unchanged, only the audio is re-timed and re-encoded. That is why the fix takes seconds even on long files and costs no picture quality.

What if the drift gets worse over time?

A fixed shift fixes a constant offset. If the audio slowly drifts, the frame rate or sample rate does not match — convert the video to a constant frame rate first (Convert Video), then apply the remaining fixed offset here.

Fix Audio Video Sync Online Free — Shift Audio by Milliseconds

Audio Sync Fixer

Fix audio that is out of sync with the video — shift the soundtrack earlier or later by milliseconds. The picture is copied untouched, so the fix is lossless and takes seconds.

Audio goes out of sync when the soundtrack starts a little before or after the picture — a recording glitch, a bad conversion, or a stream capture. EditClips.online fixes it free in your browser: upload the video, type how many milliseconds to shift the sound (positive if the audio is ahead of the lips, negative if it lags), click Process, and download. The video stream is stream-copied so the picture loses nothing; a typical fix is 100–500 ms.

How to Use Audio Sync Fixer

Upload the video whose audio is out of sync
Enter the shift in milliseconds — positive to delay the audio, negative to bring it forward
Click Process and check a spoken line or a clap in the preview
Adjust the number if needed, then download

Features

Shift the soundtrack earlier or later in 10 ms steps, up to ±30 seconds
Video is copied bit-for-bit — no re-encode, no quality loss, done in seconds
Works on MP4, MOV, MKV, WebM, AVI and other common formats
Keeps the sound quality high (AAC 192 kbps)
Free, private, no watermark

Frequently Asked Questions

How do I know whether to use a positive or negative number?: Watch a moment with a clear sound and picture cue — a clap, a door, a spoken word. If you hear it before you see it, the audio is early: use a positive value to delay it. If you hear it after you see it, use a negative value to bring it forward.
How many milliseconds should I use?: Most sync problems are between 100 and 500 ms. Start with 200, check the result, and refine — a lip-sync error under about 40 ms is not noticeable.
Does this re-encode the video?: No. The video stream is copied unchanged, only the audio is re-timed and re-encoded. That is why the fix takes seconds even on long files and costs no picture quality.
What if the drift gets worse over time?: A fixed shift fixes a constant offset. If the audio slowly drifts, the frame rate or sample rate does not match — convert the video to a constant frame rate first (Convert Video), then apply the remaining fixed offset here.

Audio Sync Fixer

How to Use Audio Sync Fixer

Features

Frequently Asked Questions

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