Free Thumbnail Anonymizer
Your image is processed entirely in your browser and is never uploaded to our servers.
Upload a thumbnail, draw rectangles over any faces or sensitive regions, click Pixelate, and download a clean PNG. The entire process happens locally — no account, no server round-trip, no watermark.
How to use it
- Click the upload area (or drag a file) to load your PNG, JPEG, or WebP image.
- Draw rectangles over the faces or regions you want to anonymize by clicking and dragging.
- Click Pixelate to apply the mosaic effect to all drawn regions at once.
- Click Download PNG to save the anonymized image. You can draw more regions and pixelate again before downloading.
Why use FatThumb's thumbnail anonymizer?
Most online image tools send your file to a server, store it temporarily, and process it remotely. FatThumb's anonymizer runs the entire pixelation algorithm in your browser using the HTML Canvas API. Your image data never travels over the network after the file chooser opens — it goes straight from your file system into your browser's memory.
This matters for creators who work with guests, interviewees, or minors. If you need to publish a thumbnail before you have consent to show someone's face, or if you're covering a sensitive topic where subjects need to remain unidentifiable, this tool lets you protect their privacy without giving a third party access to the original image.
The mosaic effect uses a block-average algorithm — each region is divided into small squares, and each square is replaced with the average colour of its pixels. The resulting image is unreadable at the block level, which is sufficient for most anonymization use cases.
FAQ
Is my image uploaded to your servers?
No. Your image is loaded directly into your browser's memory via the HTML File API and drawn onto an HTML Canvas element. The entire pixelation process runs locally in your browser. No image data is ever sent to FatThumb's servers.
What image formats are supported?
PNG, JPEG, and WebP files are supported. The download is always a PNG to preserve quality after pixelation.
How large can my image be?
There is no strict file-size limit, but very large images (above ~8000×8000 pixels) may be slow to render depending on your device's GPU and available memory.
Can I undo a pixelated region after clicking Pixelate?
Once you click Pixelate, the effect is written directly to the canvas and cannot be undone without re-uploading the original image. Draw your regions carefully before applying, and use the Undo button to remove a region before applying.
These tools are free forever.
When you're ready to generate thumbnails with your own face in 60 seconds, start free — no credit card required.
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