What this pixelate tool does
It turns a photo, or parts of it, into a mosaic of square blocks. Each block takes the average color of the pixels it covers, so the detail inside it disappears and only the rough shapes and colors remain. You can apply it to the whole image, for a retro or abstract look, or draw rectangles over the parts to hide: a face in a group photo, the license plate of a car, a house number, a name tag, the screen of a laptop or a child in the background. The blocks can be 2 to 64 pixels wide, and the same areas can be blurred instead.
The work is done by your browser, on your own device. The preview is drawn at screen size so the slider reacts at once; the download is made from the full image and has the same width and height in pixels as the original. Phone photos open the right way up, and the saved file carries no EXIF data, so the camera model, the date and the GPS position of the original are not copied.
How pixelation works
The image is covered with a grid of squares that starts in its top left corner. For each square the tool adds up the red, green and blue values of all pixels inside it and divides by their number; every pixel in the square is then set to that average. Transparent pixels count with their transparency, so a PNG with a see-through background keeps it. The grid is fixed to the image, not to the rectangle you draw, which is why a rectangle grows outward to whole blocks: the preview and the saved file then show exactly the same blocks.
A worked example: a 4,000 × 3,000 pixel photo with 20 pixel blocks becomes a mosaic of 200 × 150 blocks, 30,000 in all. A face that is 300 pixels wide in that photo is reduced to 15 blocks across, enough to see that there is a face but not whose it is. With 8 pixel blocks the same face keeps 37 blocks across, and eyes, mouth and hairline are still easy to make out. The label under the slider shows how many blocks your image gets.
| Block size | 4,000 × 3,000 photo | 1,920 × 1,080 screenshot | Good for |
|---|---|---|---|
| 4 px | 1,000 × 750 blocks | 480 × 270 blocks | A light texture, the picture stays readable |
| 12 px | 334 × 250 blocks | 160 × 90 blocks | Small details disappear, shapes stay |
| 32 px | 125 × 94 blocks | 60 × 34 blocks | Faces and plates in phone photos |
| 64 px | 63 × 47 blocks | 30 × 17 blocks | Strong mosaic, abstract look |
How safe is pixelating a face or text?
Pixelation removes detail, but it does not always remove information. Two studies are worth knowing:
- Steven Hill, Zhimin Zhou, Lawrence Saul and Hovav Shacham showed in On the (In)effectiveness of Mosaicing and Blurring as Tools for Document Redaction (Proceedings on Privacy Enhancing Technologies, 2016) that text hidden by mosaicing or blurring could be recovered with statistical models, and concluded that neither is a viable way to redact text.
- Richard McPherson, Reza Shokri and Vitaly Shmatikov describe in Defeating Image Obfuscation with Deep Learning (2016) how they trained neural networks to identify faces and recognize objects in images protected by mosaicing and blurring.
What that means in practice: large blocks hide more than small ones, and a face reduced to a handful of blocks gives such a method little to work with, but no block size turns pixelation into a guarantee. For text that must stay secret, such as passwords, account numbers, addresses or signatures, do not rely on pixelation at all. Cover it with a solid box, which the Blur Image tool offers; it replaces the pixels with one color and leaves nothing behind. Cover a little more than the sensitive part, check the result at full size before you share it, and keep in mind that other photos of the same scene can give away what you hid.
Options explained
- Whole image: every pixel goes into the mosaic. Use it for a texture, a placeholder, a teaser or an abstract version of a photo.
- Areas I draw: only the rectangles you drag over the preview are changed. The rest of the photo keeps its exact pixels. Undo last area takes the last rectangle back, Clear areas removes them all. On a phone, draw with one finger; the preview does not scroll while you drag on it.
- Pixelate or Blur: Pixelate makes square blocks of the set size. Blur softens with a radius of half the block size, so the two settings hide about the same amount of detail.
- PNG or JPG: PNG keeps every pixel outside your areas exactly as it was and keeps transparency. JPG is smaller for photos and compresses the picture again with the quality you set; transparent areas turn white.
How to pixelate an image
- 1Drop a photo on the box, choose one from your device or paste it. HEIC photos from an iPhone work too.
- 2Choose Whole image, or Areas I draw and drag rectangles over the faces, plates or names to hide.
- 3Set the block size until the detail is gone in the preview. Switch to Blur if you prefer a soft look.
- 4Choose PNG or JPG and press Download image. The file is saved at the full size of your photo.
For ellipses, a brush and a solid box, use Blur Image. To make the saved file smaller, run it through the image compressor, and to check what data a photo still carries, use the EXIF viewer and remover.
Sources
- Hill, Zhou, Saul, Shacham: On the (In)effectiveness of Mosaicing and Blurring as Tools for Document Redaction, PoPETs 2016
- McPherson, Shokri, Shmatikov: Defeating Image Obfuscation with Deep Learning, arXiv 2016
- MDN: HTMLCanvasElement.toBlob(): PNG is always supported, JPEG with a quality value where the browser offers it
- W3C PNG Specification, third edition: truecolor with alpha (color type 6), section 11.2.1
Related guides
- How to Compress a Photo Under 100 KB
- HEIC Photos Explained: Open, Convert, Avoid
- How to Write Alt Text: Rules, Examples and Empty Alt
Frequently asked questions
Is my photo uploaded?
No. Your browser opens the photo, pixelates it and saves the new file on your own device. Nothing is sent to a server, which matters most for the kind of pictures people pixelate.
How do I pixelate only a face or a license plate?
Choose Area, then drag a rectangle over the face or the plate on the preview. Draw as many rectangles as you need; Undo last area takes the last one back and Clear areas removes them all. Then press Download image.
Which block size should I use?
Large enough that you cannot make out the detail any more in the preview at full size. For a face in a phone photo, 24 to 40 pixel blocks usually do it. A face that is only 60 pixels wide with 8 pixel blocks still shows its shape. When in doubt, go bigger: the slider goes up to 64 pixels.
Is pixelation safe for passwords, account numbers or addresses?
Not reliably. Studies have shown that text hidden by small blocks or a light blur can sometimes be read again, especially when the font is known. For anything that must stay unreadable, do not pixelate it: cover it with a solid box in the Blur Image tool on this site, which replaces the pixels with one color and leaves nothing behind.
Does the saved photo keep its full size?
Yes. The preview is drawn smaller to stay quick, but the download is made from the full image, so it has the same width and height in pixels as your original. Only on iPhone and iPad, where Safari cannot draw very large canvases, an image above the limit is scaled down, and the tool says so.
Does the saved file still contain the camera data and location?
No. The new PNG or JPG is written by the browser from the pixels alone, without the EXIF data of the original. The camera model, the date and the GPS position are not copied. Your original file is not changed.
What is the difference between pixelate and blur?
Pixelate replaces every square block with one average color, the mosaic look. Blur mixes each pixel with its neighbors, so the picture goes out of focus. Both hide detail and both hide more at a higher setting. Here you can switch the areas between the two; the whole image can be pixelated or blurred as well.