Mosaic - Photo Mosaic Editor
Mosaic is a quick way to hide parts of a picture before you share it. Open a photo, drag rectangles over the faces, licence plates, house numbers, name tags or screen contents you want to obscure, and apply a pixel mosaic to just those areas. The rest of the image stays untouched.
A slider sets the size of the mosaic blocks, from fine squares that soften details to coarse blocks that make text and faces unrecognisable. You can mark several areas, undo the last one or clear them all before applying, and then download the finished image.
Everything happens inside your browser. The photo is not uploaded anywhere, which matters when the reason you are editing it is privacy.
The app runs entirely in your browser. What you enter is saved only on this device.
How to use Mosaic
- Open a photo. Tap Gallery to choose an image. On a phone browser, Camera can take a new picture; on a computer it opens a file chooser.
- Set the mosaic size. Move the Mosaic Size slider between Fine and Coarse. Larger values make bigger blocks that hide more detail.
- Mark the areas. Drag across the image to draw a rectangle over each part you want to hide. You can draw as many rectangles as you need.
- Correct mistakes. Use Undo Last to remove the most recent rectangle or Clear All to start the selection again.
- Apply the mosaic. Tap Apply Mosaic. The processed image appears with a confirmation message. Check that every sensitive detail is covered.
- Save the result. Tap Save to Gallery to download the image as a PNG file, or Reset to start over with the original.
Features
- Drag to select rectangular areas
- Any number of areas per image
- Adjustable block size from fine to coarse
- Undo last selection or clear all
- Mosaic applied at the photo's full resolution
- Download the result as a PNG file
- Processing stays in your browser
- Built-in help and interface in many languages
Hiding private details in photos properly
What to look for before sharing
Photos often reveal more than intended. Before posting, scan the whole picture, not just the subject: faces of bystanders and children, car number plates, house numbers and street signs near your home, school uniforms and name badges, documents, tickets and boarding passes with barcodes, and screens showing messages or account details. Reflections in windows and mirrors can also show things you did not mean to include.
Choosing a block size
A mosaic works by replacing each block of pixels with a single colour. Small blocks blur fine detail but can leave large shapes, such as big letters, guessable. For text, numbers and faces, choose blocks at least as large as a single character or facial feature, and make the selected area a little larger than the item itself so that edges are covered too.
Mosaic versus solid boxes
Pixelation keeps the picture looking natural and is fine for most social sharing. For highly sensitive information, such as identity numbers, bank details or passwords, a solid filled box is safer, because there is no remaining pattern that could hint at the original content. Better still, avoid photographing that information at all.
Respecting other people
Many people prefer not to appear online without being asked, and in some places publishing identifiable images of others is restricted. Pixelating faces in crowd shots, at school events or in photos of strangers is a considerate habit. When in doubt, ask permission or leave the person out of the frame.
Check the final file
Always look at the saved result at full size before sending it. Zoom in on each edited area to make sure nothing is readable. Mosaic saves a new PNG image from the edited pixels, so the original photo on your device is not changed; share only the new file.
Frequently asked questions
Are my photos uploaded?
No. The image is loaded, edited and saved inside your browser on your device. Nothing is sent to a server and nothing is kept after you leave the page.
Where does the saved image go?
On the web, Save to Gallery downloads a PNG file named like mosaic_1234567890.png to your browser's download location. On a phone you can then move it to your photo library.
Can I use shapes other than rectangles?
No. Areas are selected as rectangles. Draw several overlapping rectangles to cover irregular shapes.
Can someone reverse the mosaic?
The original pixels in the selected areas are replaced, so they are not stored in the new file. Very small blocks may still leave recognisable shapes, so use a coarser size for text and faces.
Why is the PNG larger than my original photo?
PNG is a lossless format and is usually larger than a camera JPEG. The image keeps the original resolution.
What is different from the phone app?
The editing is the same. The iPhone and Android apps save straight to the photo library and show ads that a subscription removes; the web version downloads the file and has no ads or purchases.
Limitations of the web version
- Results are downloaded as PNG files instead of saved to a photo library
- Only rectangular selections
- Edits are not kept after the page is closed
- Very large photos may process slowly on older devices
Phone app
Mosaic is also available as an app for phones and tablets: