🟦 Image Mosaic / Blur
Drag to select any region and apply mosaic or blur. Useful for hiding faces, license plates, and personal info. Processed in-browser via Canvas API.
🔒 About Privacy
- ・All processing happens entirely in your browser
- ・Image data is never sent to any server
- ・No storage logs, no upload history, no database
- ・No signup, no login, no payment ever
Drag & drop, click to select, or paste an image
💡 Drag on the image to select a region — applied automatically
📖 Where people get stuck
Select any region by dragging and apply a mosaic, a blur or a solid black fill, with rectangular, elliptical or freehand selection. Processing uses the Canvas API entirely in the browser. If the purpose is to hide something, which effect you choose is the decisive question: a mosaic or a blur weakens the information without destroying it. There are documented cases of recovery, so do not use them for anything that genuinely must not be seen.
| Case | What happens | What to do |
|---|---|---|
| Mosaic and blur can be reversed | A blur averages neighbouring pixels, and averaging does not fully destroy information — something close to the inverse operation can recover an approximation of the original. A mosaic is worse still: where the set of possible strings behind it is small — a numeric licence plate, a product code in a fixed format, a card number — you can simply mosaic every candidate and compare. That is brute force, and it needs no sophisticated technique. A face obscured with a swirl distortion has in fact been reconstructed and used in a criminal investigation. | Use the solid black fill for anything that must genuinely be hidden. Filling replaces the pixels in that region with a single colour, so the original information is gone completely — that is the only approach that is safe in principle. Understand a mosaic or a blur as a presentational effect for making something less noticeable, not a feature for making it unreadable. As a rule of thumb: a mosaic is fine when the goal is consideration, such as blurring passers-by in a published photograph; for an address, a name or a number — anything where disclosure is a problem — the black fill is the only option. When in doubt, fill it black: this is not a place to trade safety against appearance. |
| The masked area is not enough to prevent identification | Hiding only the face still leaves hairstyle, build, clothing, accessories, the buildings behind, a reflection in a mirror or window, a lanyard badge, or the document in someone hand. In a photograph of a document, removing the name leaves the address, phone number, reference number, an official seal and the form layout itself as clues. A single missed spot is fatal, and it is exactly what you are least likely to notice yourself — information you already know does not register visually, so you overlook what is obvious to anyone else. | Before you start, put into words what you are protecting against. Not wanting an acquaintance to recognise someone and not wanting the general public to identify them call for entirely different coverage. For the former, the face alone is not enough; for the latter, retaking the photograph or cropping down to only what is needed is more reliable (image crop tool). Always have someone else look at it before you publish — simply asking can you tell who this is surfaces clues you could not see. Reviewing it yourself after a gap also helps, since fading memory brings you closer to a stranger eye. |
| The unedited original survives somewhere | Even when the editing itself is correct, the original can leak because you attached it alongside, an unedited screenshot is still sitting in a chat, or a cloud backup captured the original. Harder to anticipate is the behaviour of the editing application itself: the Windows Snip and Sketch tool and the Pixel screenshot editor both had a defect that left the original image data at the end of a file you had cropped — known as aCropalypse. The assumption that saving over a file removes what was there does not always hold. | Check the output filename (_masked) and hand over only that. This tool never overwrites your original and always saves under a new name, so that particular accident cannot happen here. As a final check before publishing, open the file you are about to send and look at it — the file you meant to edit and the file you actually attached being different is a startlingly common mistake. If the file size looks oddly large, suspect leftover data. For extra certainty, take a fresh screenshot of the edited image: by construction, nothing beyond what is on screen can be in it. |
Going through a canvas strips all EXIF from the output — losing GPS coordinates and the capture timestamp is a welcome side effect before publishing. Other ways of hiding things have traps, though. Covering something with a black rectangle in a PDF, a Word file or a slide deck is entirely ineffective: the shape can be moved, and if it is text underneath it can be selected and copied. This has caused real disclosures again and again, including repeatedly in documents published by public bodies. To remove content from a document, export it to an image first and edit the image — it takes longer, and it is the only reliable procedure. One more thing: loading an animated GIF or WebP processes only the first frame, so this tool cannot help you hide something inside a video or an animation.
📖 How to Use
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1
Load an imageDrag and drop, click to select, or paste from clipboard with Ctrl+V.
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2
Choose effect and strengthChoose mosaic / blur / black fill. Use the slider to adjust block size.
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3
Drag a region to applyDrag on the image. The effect is applied to that region as soon as you release. Drag multiple times for multiple regions.
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4
DownloadDownload as PNG or JPEG. Filename gets _masked suffix.
❓ Frequently Asked Questions
Is my image uploaded to your server?
Can the mosaic be reversed?
What image formats are supported?
🔗 Related Tools
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