Image Mosaic & Blur Tool

A free tool to drag-select any area of an image and apply a mosaic (pixelation) or blur effect. Perfect for hiding faces or license plates before sharing photos on social media. Processing happens entirely in your browser; images are never uploaded to a server.

Tips

  • You can adjust the block size (mosaic) or blur strength with the slider before dragging. Larger values make the original content harder to make out, so choose a larger value if you need to hide something reliably.
  • To hide several faces or license plates in the same photo, just drag over each area one by one — every drag is applied immediately, so you can repeat as many times as needed.
  • The "Undo" button removes every mosaic or blur applied so far and restores the original image, which is handy if you selected the wrong area.
  • Downloaded images are always saved as PNG, so any transparency in the original is preserved in the result.
  • The selection area is always processed against the image's original resolution, not its on-screen display size, so accuracy is unaffected even when the preview is scaled down.

Frequently Asked Questions

Both make the original content unreadable, but mosaic averages pixels into visible blocks, so it is immediately obvious to viewers that something was hidden, while blur gives a softer, more natural-looking result. If reliably hiding information matters most, mosaic with a larger block size is the safer choice.

No, this tool does not use AI-based face detection — it only applies mosaic or blur to the rectangle you manually drag over the image. Skipping automatic detection keeps the browser workload and dependencies light, and avoids the risk of misdetection (missing the area you actually wanted hidden, or flagging an unrelated area).

No. Once mosaic or blur has been applied and the image downloaded, the original pixel values cannot be recovered from the averaged data. The larger the block size or blur strength, the harder recovery becomes, so you can share the result with confidence for privacy purposes — though it is still a good idea to keep the original image on hand.

No. Loading the image, applying mosaic or blur, and downloading the result all happen entirely inside your own browser (client-side); your image data is never transmitted to any external server.
ツールくん

Side Note — Which hides better, mosaic or blur?

The pixelated mosaic used to cover faces on Japanese television is actually a broadcasting-industry convention rather than a legal requirement. Overseas news footage more often uses a soft "blur" effect for the same purpose, and this difference is often attributed to varying broadcasting cultures and audience expectations across countries.

Technically, mosaic (pixelation) is a simple process that averages the colors within a region and replaces them with uniform blocks — and precisely because it is so simple, it makes it visually obvious at a glance that information has been removed. Blur, on the other hand, blends neighboring pixels together with weighted averaging, producing softer edges that look less jarring, but it tends to give less of the "this can absolutely not be read" confidence that a large mosaic block size provides.

There have been research reports and real-world cases of recovering the original license plate numbers or text from images with weak mosaic or blur applied. If the block size or blur radius is too small, comparing multiple processed images or inferring from surrounding context can sometimes reveal the original content, so anything you genuinely want to hide should use a larger block size or stronger blur.

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