Question 1

Is this free with no watermark?

Accepted Answer

Yes — completely free, no watermark, no account required, no file size limits beyond browser memory.

Question 2

Does my video get uploaded?

Accepted Answer

No. FFmpeg WebAssembly runs 100% inside your browser. Your video and music never leave your device.

Question 3

What is the difference between the audio modes?

Accepted Answer

'Background Music' removes original audio and adds only your music. 'Mix with Original' blends your music with the existing video audio (voiceover, dialogue etc). 'Replace Audio' is identical to Background Music but more descriptive for some use cases.

Question 4

My music is shorter than my video — what happens?

Accepted Answer

Choose 'Loop Music' to seamlessly repeat the track to fill the video. Or 'Trim Video' to cut the video to the music's length. Or 'Play Once' to let the video go silent after the music ends.

Question 5

What is EBU R128 normalisation?

Accepted Answer

It normalises your audio to -16 LUFS — the loudness standard used by YouTube, Instagram, TikTok, and Spotify. This ensures your video won't sound too loud or too quiet on any platform.

Question 6

Can I start the music partway through the video?

Accepted Answer

Yes. Use the 'Music Start Delay' option to set a delay in seconds — for example '5' to let 5 seconds of original video audio play before the music begins.

Question 7

Can I use only part of my music file?

Accepted Answer

Yes. Set 'Music Clip Range' start and end times to use only the chorus or skip the intro. Combine with Music Start Delay for precise sync.

Question 8

What video formats are supported?

Accepted Answer

MP4, MOV, WEBM, MKV, AVI, M4V, FLV, WMV, TS and 3GP. Output is MP4, WebM, MKV or MOV.