Blur an image
Blur a whole image to make a soft background, a frosted-glass panel or a low-detail placeholder. The radius is the standard deviation of the Gaussian, so 2 is a gentle softening and 40 turns a photograph into colour fields. Edge pixels are handled properly, so the border does not fade to white.
How to use the Blur Image
- Add the images you want to soften.
- Set the radius. Start around 8 and adjust — larger images need larger radii for the same visual effect.
- Click Blur. The whole frame is blurred evenly.
- Download the results individually or as a ZIP.
What the radius actually means
This tool uses the browser's canvas blur filter, which applies a true Gaussian blur where the number you set is the standard deviation of the Gaussian function in pixels. Visually, detail smaller than roughly three times that value disappears. The important consequence is that the right radius depends on image size, not on what the image contains: a radius of 10 on a 4000-pixel-wide photo is a mild haze, while the same 10 on a 500-pixel thumbnail obliterates it. If you are blurring a batch of different sizes, resize them to a consistent width first.
The washed-out border problem
A naive canvas blur samples beyond the edge of the image, where there is nothing, and averages in that emptiness. The result is a pale or semi-transparent band around the whole frame that gets wider with the radius. This tool avoids it by first extending the outermost row and column of pixels outwards to build a margin three times the radius, blurring that padded image, and then cropping back to the original dimensions. The edges therefore stay as solid as the middle.
Blur is not redaction
This matters. A blur is a reversible mathematical operation in principle, and the information is still partly present in the output file. Published research has repeatedly recovered blurred and pixelated text when the font, layout and character set were known. If you are hiding a name, an address, a card number or a licence plate in something you are going to publish, do not rely on blur. Cover it with a solid opaque shape, or crop it out of the frame entirely. Heavy pixelation is a better second choice than blur, but a solid block is the only genuinely safe one.
Good uses for blur
- Backgrounds. Blur a photo, lay text over it, and the text becomes readable without a dark overlay.
- Placeholders. A tiny, heavily blurred copy of an image makes a lightweight preview while the real file loads.
- Depth. Softening a busy background approximates a wider aperture and pushes the subject forward — though on a fully blurred image the subject softens too.
- Deliberate abstraction. Large radii turn any photograph into a smooth gradient that works well as a banner or card background.
Formats and size
PNG input stays PNG, WebP stays WebP, everything else becomes JPG. Blurred images compress extremely well — a heavily blurred JPG is often a tenth the size of the original, because there is very little high-frequency detail left to encode.
Frequently asked questions
Can blurred text be read again?
Sometimes, yes. Recovering blurred or pixelated text is a well-documented attack when the font and layout are predictable. Use a solid block for anything sensitive.
Why does my blur look weaker than expected?
Radius is measured in pixels, so a large photograph needs a much larger radius than a thumbnail for the same visual effect. Try resizing first, or raise the radius.
Can I blur only part of the image, such as a face?
Not here — this blurs the whole frame. The pixelate tool has region controls and destroys detail more thoroughly, which makes it the better choice for faces.
Does the border go pale?
No. The edge pixels are extended outwards before blurring and the result is cropped back, so there is no washed-out band around the frame.
Privacy
This tool runs entirely inside your browser using WebAssembly and the Canvas/File APIs. Your files are never uploaded to ToolFlint or any third party; you can verify this in your browser's network tab or by switching to airplane mode after the page loads. Read how we process files.
Last updated 2026-09-23.