# Blur Faces in a Video — Free, Local, No App

> Blur faces in an MP4 or MOV video — draw a box over each face and export a new file with those pixels blurred. Runs locally, no upload, no watermark, no app.

Source: https://toolpantry.app/face-blur-video

## About

Draw a box over each face and export a new video with those pixels blurred — baked in, not an overlay. No upload, no watermark, no app install.

## Quick answer

How do I blur faces in a video for free? Load the MP4 or MOV, pause on a frame where the face is visible, and drag a box over it (or press Detect faces on Chrome). Set the blur strength, then press Blur & export — the box is blurred on every frame and written into a new MP4, entirely on your device.

## How it works, and what "baked in" means

The tool decodes each frame with your browser's media pipeline (WebCodecs), draws the frame to a canvas, applies a gaussian blur to the pixels inside your boxes, and re-encodes everything to a new MP4. Because the blur happens *before* encoding, the exported file contains no sharp pixels in that region — it is not a sticker or an overlay that a viewer could remove. The original file on your device is never touched, so keep it somewhere private if it contains the unblurred footage.

## Getting a good result

- **Scrub first** — pause on a frame where the face is biggest or most visible, and draw the box there; it will cover the whole clip
- **Cover the path** — for someone walking through the frame, one tall box over their route beats several small boxes
- **Strength by resolution** — 16–20 px is plenty at 720p; scale up for 1080p/4K. When in doubt, stronger is safer for privacy
- **Check one frame** — after export, scrub the result once to confirm nothing peeks out at the edges

## Honest limits

Boxes are fixed for the whole clip — this tool doesn't track faces frame by frame, so a fast-moving face may leave the box. Auto-detection runs on Chrome (Shape Detection API) and only on the frame you're looking at; on other browsers, drawing boxes manually works the same. Input is MP4/MOV with H.264 or HEVC video; output is always MP4 (H.264 + AAC). Re-encoding costs a little quality — for a privacy export, that's usually a trade worth making. Blurring a photo instead? Use the [face blur tool](https://toolpantry.app/face-blur.html) for images, and if you just need to shrink a clip, the [video compressor](https://toolpantry.app/compress-video.html) is the right tool.

## Notes

Draw one box per face; the box covers the same spot on every frame. For moving faces, make the box cover the area they move within. Re-encoding a 1-minute clip typically takes 10–40 seconds on a laptop.

## FAQ

**How do I blur a face in a video?**

Load the MP4 or MOV, scrub to a frame where the face is visible, and draw a box over it — on Chrome you can also press Detect faces to place boxes automatically. Set the blur strength and press Blur and export. The blur is applied to that area for the whole clip, and nothing is uploaded.

**Does it track the face as it moves?**

No — the boxes you draw are applied to every frame. For a face that moves, draw a box that covers the area it moves within. For talking-head clips where the face stays in place, a snug box works fine.

**Is the blur real, or can it be reversed?**

The pixels in that region are replaced with a gaussian blur before re-encoding, so the exported file no longer contains the sharp original pixels — the blur is baked in. Keep in mind the source file on your device is untouched and still sharp; only the exported copy is blurred.

**Which formats are supported?**

Input: MP4, MOV, and M4V (H.264/HEVC video with AAC audio). Output: MP4 with H.264 + AAC. The re-encoding uses WebCodecs, so Chrome, Edge, and Safari 17+ are required — Firefox support is still rolling out.

**How strong should the blur be?**

At 720p, a 16–20 px blur makes a face unidentifiable while keeping the video looking natural. For 1080p use 20–28 px, and for 4K go higher — the stronger the blur, the safer the privacy.