How to blur a face in an MP4 video
An MP4 file is a container: the video codec inside determines whether a browser can decode and re-encode it. FaceBlur accepts MP4 files up to 90 MB and automatically covers every face it detects.
Blur an MP4
- Choose the MP4 and wait for the preview.
- Play and scrub the clip to inspect automatic masks.
- Select mosaic, blur, or solid, then tune strength and safety margin.
- Export and watch the complete downloaded file.
Why an MP4 might export as WebM
MP4 export requires a browser and device that can encode AVC video. When that encoder is unavailable, FaceBlur attempts WebM instead. The visual treatment is the same, but the container and codec differ. Current Chrome, Edge, and Safari generally provide the strongest media support.
MP4 troubleshooting
| No preview | The codec inside the MP4 may not be supported by that browser. Try a current browser or transcode the source to H.264. |
|---|---|
| Export unavailable | The device lacks a supported MP4 or WebM encoder. |
| Several people covered | Expected: the tool applies the same settings to every detected face and does not select one person only. |
| Audio identifies someone | Enable Remove audio before export. |
Container is not a guarantee. Two files ending in .mp4 can use different codecs. Never rename an extension to convert video.
Process an MP4
Free automatic face detection, browser export, and no watermark.
Choose an MP4