Image Mosaic

What is a mosaic effect?

A mosaic effect is a censoring and artistic technique that divides an image into a grid of square tiles, replaces every pixel in each tile with the average colour of that tile, and then draws thin grid lines between the tiles to make the tiling pattern explicitly visible. It is the classic broadcast-TV censoring effect used to obscure faces, license plates and sensitive content. The grid lines are what distinguish a mosaic from plain pixelation: they make it immediately obvious that the region has been deliberately obscured, rather than simply low-resolution.

This tool runs entirely in your browser. When you upload an image, it is decoded through the Canvas API and displayed in the preview. As you drag the tile-size slider, the tool reads the raw pixel buffer, walks the image in tile-sized steps, computes the average colour for each tile, fills the tile with that colour, and then overlays a semi-transparent grey grid along the tile boundaries. The preview updates instantly, and the result can be downloaded as a PNG file. Nothing is ever uploaded to a server.

Mosaic vs pixelate

Mosaic and pixelation use the same underlying block-averaging algorithm, but the mosaic effect adds visible grid lines between tiles. This seemingly small difference has a big impact on perception: the grid lines signal "this area has been censored" far more clearly than flat blocks alone, which is why mosaic is the standard for broadcast privacy. Pixelation without grid lines can sometimes look like a genuine low-resolution image, which may cause confusion about whether the effect was intentional. For artistic purposes, some designers prefer the cleaner look of pixelation, while others like the structured, tiled appearance of mosaic.

When to use mosaic

Mosaic censoring is useful in a wide range of scenarios. Common use cases include:

How to apply mosaic to an image

Mosaic censoring is useful in a wide range of scenarios. Common use cases include:

• Faces and identities. Obscure faces of people who have not consented to being in a photo or video, such as bystanders in street photography.
• License plates and vehicle IDs. Blur or mosaic license plates before sharing photos of cars in public spaces.
• Sensitive text and documents. Hide passwords, personal information, or confidential screen content in screenshots and tutorials.
• Minors and vulnerable individuals. Protect the identities of children or vulnerable people in news and documentary content.
• Artistic tiling. Use a small tile size for a decorative, stained-glass-like effect on photos and illustrations.

Whenever you need to clearly signal that a region of an image has been censored, mosaic is the most universally understood visual cue.

Mosaic for privacy and censoring

Applying a mosaic effect with this tool takes only a few seconds and runs entirely in your browser — no uploads, no sign-up, no watermark. Follow these steps:

1. Upload your image. Click the upload area or drag and drop a JPG, PNG, WebP, GIF or BMP file. The image is decoded and previewed instantly.
2. Adjust the tile size. Drag the slider from 4 to 32 pixels. A small value keeps more recognisable detail, while a large value produces a heavier censoring effect. The preview updates in real time.
3. Download the result. Click "Download Mosaic Image" to save the mosaic PNG. The original file stays untouched on your device.

Because every step runs locally through JavaScript, your image is never sent to a server. This makes the tool completely private, fast and suitable for sensitive or confidential images.