Video Watermark stamps a logo, a signature or a QR code image onto a fixed spot in a video, so a clip can be traced back and a re-upload is less attractive. It is the “Add watermark” tab of the audio/video workbench and composites with ffmpeg's overlay filter: colorchannelmixer first scales the whole watermark image to the opacity you asked for, the image is then resized proportionally to “video width × percentage”, and finally it is pasted into one of the nine grid positions, always 16 pixels from the edge.

A PNG with an alpha channel is the right format for the watermark — transparent areas let the picture through. A JPG has no alpha, so it lands on the frame as a solid rectangle. Every frame is re-encoded (H.264 CRF 20) while the audio track is copied through untouched wherever it can be.

1. 01Add a video and select it— switch to the “Add watermark” tab.
2. 02Upload the watermark image— drop in or pick a PNG / WebP / JPG; the panel previews its transparent areas over a checkerboard.
3. 03Set position and style— click one of the nine cells (top left, top centre, top right, middle left, centre, middle right, bottom left, bottom centre, bottom right; bottom right by default); drag “Watermark width (share of video width)” between 5%–50% (20% by default) and “Opacity” between 10%–100% (80% by default).
4. 04Add and download— click “Add watermark”, then download <original-name>_watermarked.mp4 (MOV / MKV / M4V keep their extension, other containers come out as .mkv).

One static image

one image at a time, one fixed position for the whole clip; no text watermark, no multiple watermarks and no “ticker” watermark that travels over time

A fixed grid of positions

nine spots with a fixed 16 px margin, and no way to type arbitrary coordinates

Re-encoding

H.264 CRF 20 preset fast, so the wait scales with the clip length; AV1 sources cannot be decoded; AAC / MP3 / AC3 / Opus / Vorbis / FLAC audio is copied, anything else is converted to AAC 128 kbps

Watermark size

scaled as a share of the video width, minimum 16 px; a very low-resolution logo stretched to 50% looks soft

What it does not do

it does not remove watermarks (use “Video watermark remover”), it does not burn in subtitles, and it does not overlay a second video as picture-in-picture

The video and the watermark image are composited locally in the browser by ffmpeg.wasm and are never uploaded; the first run downloads about 31 MB of engine files from a CDN (the site's asset domain or jsDelivr), and that request does not include your files.