Pixelate an Image (Mosaic)

How it works

Choose your photos, set the block size with the slider and press Pixelate. The tool divides the image into square blocks and paints each block with the average of the colours inside it; the square edge scales with the image resolution, so the same setting produces the same look on an 800-pixel screenshot and a 4000-pixel phone photo. As a working example: level 5 on a photo with a 3000-pixel long edge produces 150-pixel squares — only 20 blocks side by side, leaving no text or face recognisable. Levels 1-2 instead give a fine pixel texture that keeps the photo readable, which is the range to use for a pixel-art look. Each result line shows the before-and-after file size and the actual square edge in pixels. A JPG source comes back as JPG; PNG and WEBP sources come back as PNG with transparency preserved, and you can process several photos in one batch. The blocking runs entirely in your browser — the image is never sent to any server.

This tool is also known as pixelate image online, pixelate a photo, mosaic censor effect, blur out text in image, pixel art from photo.

What is Mosaic (pixelation)?

A mosaic divides the image into fixed-size square blocks and fills each block with the average colour of the pixels inside it. Because everything within a block collapses into one colour, nothing smaller than the square edge — a letter, an eye, a digit on a licence plate — exists in the output at all. Seen from a distance the picture still reads: the patches of colour preserve the composition. The same operation serves television face censoring and pixel art alike, only at different block sizes — larger squares hide more, smaller ones turn the effect into an aesthetic texture.

What is Block (square) size?

The one setting that matters in a mosaic is the square edge in pixels, and the right value depends on the image resolution: a 30-pixel square is a fine texture on a 4000-pixel photo but obliterates a 400-pixel thumbnail completely. This tool therefore scales the square edge as a fraction of the longer side rather than using absolute pixels — the 1-10 slider produces the same proportional look on every photo. The actual edge chosen for each file is printed in the result line in pixels, so you can compare settings between runs.

What is the difference between pixelating and blurring?

A mosaic destroys information in blocks: detail smaller than the square simply never reaches the output, and the hard-edged result openly tells the viewer that something was deliberately covered — it is the conventional censor mark in documents and news imagery. A blur instead smears pixels across a wide area; the surface stays smooth and natural, which is why blurs win for aesthetic jobs like cover images. In hiding power both depend on the setting: a fine-block mosaic can be partially reversed by pattern matching, and a light blur by sharpening. When you pixelate to censor, choose a large block size and zoom into the result to check it yourself.

A fine mosaic is not enough for privacy

Detail smaller than the square is erased completely — but with small squares, little is erased. Text pixelated at levels 1-2 can be partially recovered by pattern-matching attacks that compare the block pattern against candidate renderings; on content with a limited alphabet (digits, licence plates, known fonts) these attacks work surprisingly well.

To genuinely hide something, make the square larger than the detail you are hiding: a face should span only a few blocks, and a single block should swallow several letters at once. Zoom into the downloaded file and check; your original is untouched and the output downloads separately with a -mozaik suffix, so trying several sizes is safe.

Which level for which job?

The right block size depends on what the mosaic is for. Trying a few settings takes seconds; these ranges are a starting point.

• Level 1-2 → pixel-art texture; the photo stays recognisable
• Level 3-4 → stylised, semi-abstract look for covers and banners
• Level 5-7 → hiding text and faces in a screenshot
• Level 8-10 → censoring documents, plates and faces; only colour patches remain

Frequently asked questions

How do I pixelate a photo?

Choose the photo from the box, set the block size with the slider and press Pixelate. The converted file downloads with a -mozaik suffix, and you can process several photos at once.

Can I pixelate just a face or a licence plate?

This tool pixelates the whole frame; there is no region selection. To hide a single area, crop the photo down to that area first with the crop tool and pixelate the crop, or use a large block size to cover the entire image.

Is my photo uploaded to a server?

No. The pixelation runs entirely inside your browser; neither the file nor its name or content is sent anywhere. That is why it is safe to use on IDs, documents and plates.

Can a mosaic be undone?

Not from the downloaded file — detail inside a block is never written into it. Fine-block mosaics can however be partially reconstructed by pattern matching, so choose a large block size when censoring. Your original file stays untouched.