Pixelate an image or part of one
Apply a mosaic to any area of a photo — or the whole picture — with an adjustable block size, live preview and no watermark on the download.
- Runs in your browser
- Files are never uploaded
- Free, no account
What pixelation actually does
A mosaic filter divides the selected area into a grid, averages every pixel inside each cell, and paints the cell that single colour. Nothing clever happens: the detail inside a cell is replaced by its mean. That is why the only setting that really matters is the cell size, and why the useful question is not “how strong is the effect” but “how many cells wide is the thing I am hiding”.
How to pixelate part of an image
- Drop in the image — photo, screenshot or scan.
- Drag a rectangle over each area you want to obscure. Add as many as you like; the table below the canvas lets you fine-tune each one numerically.
- Move the strength slider until the area is unreadable. Strength is measured against the box you drew, so small selections automatically get proportionally larger blocks.
- Export as PNG for screenshots and graphics, JPG for photos.
Choosing a block size
| Cells across the selection | Effect | Verdict |
|---|---|---|
| 20 or more | Looks censored, but shapes and letters are still legible | Decorative only |
| 10–20 | Faces unrecognisable at a glance, text still guessable | Weak |
| 4–8 | Nothing but a colour gradient remains | The sensible default |
| 2–3 | Effectively a solid colour | Use a solid block instead — it is simpler and honest |
Pixelation is not encryption
This is worth being blunt about, because a lot of pages selling “secure pixelation” are not. Mosaic is a deterministic, publicly known function with a very small output space. If the hidden content comes from a short, predictable set — a six-digit account number, a licence plate, a date of birth, a name from a staff list — an attacker can render every candidate, apply the same mosaic and match the result. Researchers have demonstrated exactly this against pixelated text in redacted documents and screenshots.
Faces are a different case: there is no small candidate set for a human face, and at four to eight cells across, nothing usable survives. So: mosaic for faces and scenery, solid blocks for anything you could have typed. The censor tool opens in block mode for exactly that reason.
Pixelating the whole image
Switch on Apply to the whole image and the boxes are ignored. Two common reasons to do this: producing a low-information placeholder or teaser of a screenshot you are not ready to publish, and creating a deliberately abstract background from a photograph. The block size is then relative to the whole frame, so the same strength value gives a much coarser grid.
Quality notes
- The export is full resolution. The preview is scaled down to fit your screen, but the mosaic is recomputed at native size on export, from the same fractional coordinates — so what you see is what you get, just bigger.
- Cells are hard-edged on purpose. Smoothing is switched off when the reduced copy is scaled back up, otherwise the browser would interpolate the blocks and quietly leak some of the detail you meant to remove.
- Metadata is dropped. Re-encoding from raw pixels discards EXIF, GPS and the embedded thumbnail — the thumbnail being the one that most often still shows the unpixelated original.
- Prefer PNG for screenshots. A mosaic is large flat blocks, which PNG stores extremely efficiently; JPEG would add ringing along every block edge.
Related tools
Use Blur Face in Photo when a soft blur reads better than a grid, Censor Image when the content is text, and Blur License Plate for vehicle photos. If the pixelated screenshot then needs to fit an upload limit, reduce it to any KB target.
Questions
How large should the mosaic blocks be?
Big enough that no feature survives. A useful rule: the masked area should end up no more than 6–8 blocks across. The strength slider is measured against the box you drew, so a small box automatically gets proportionally larger blocks.
Is pixelation as safe as blurring?
For text it is weaker. Short, predictable strings such as a licence number or a date of birth have been recovered from coarse pixelation by brute-forcing every candidate through the same filter. For anything textual, use the solid-block mode instead.
Can I pixelate the whole image?
Yes — switch on “Apply to the whole image” and the boxes are ignored. That is useful for creating a placeholder or a low-information preview of a screenshot.
What resolution does the export use?
The full resolution of the original. The mosaic is recomputed at export time from the fractions you drew, so the result is identical to the preview but at native size.