Blur background online
Give any photo the portrait-lens look after it was taken. The subject stays crisp, the background melts, and bright spots bloom into bokeh discs, without the halo that cheap blur leaves around hair.
- Free, no sign-up
- Runs in your browser
- Nothing uploaded
Drop a photo to blur its background
or paste from clipboard · JPG, PNG, WebP
Why phones blur in software: the optics
Background blur comes from the circle of confusion: a point that isn't in focus lands on the sensor as a small disc instead of a dot. The disc's size grows with focal length squared and shrinks with the f-number. That's why a 50 mm lens at f/1.8 on a full-frame camera melts a background, while a phone's tiny 7 mm lens at a similar f-number barely softens it. Compare them yourself:
- Blur disc on sensor
- 0.570 mm
- Share of frame width
- 1.58%
- On a 4000 px photo
- 63 px
Classic portrait look. Lights turn into discs.
The formula is the thin-lens approximation used in photography texts such as Sidney Ray's Applied Photographic Optics: blur disc = f² / (N · (s − f)) × |d − s| / d, where f is focal length, N the f-number, s the focus distance and d the background distance. Phone portrait modes, and this tool, skip the physics: they find the subject with a segmentation model and blur everything else. If you want the real mechanics behind effects like these, try the interactive explainers on ahaboo.
Choosing a blur strength
- Headshots and profile pictures: strong blur (25–40) so the face is the only thing in focus.
- Product photos in context: light blur (6–12) keeps the setting readable but calm.
- Group photos: keep it gentle. Heavy blur behind a group looks fake because real lenses can't blur that much with several people in focus.
Questions people ask
How do I blur the background of a photo online?
Drop the photo above. The AI separates the subject from the background, and the background is blurred while the subject stays sharp. Use the slider for strength and turn on Lens bokeh to make bright spots bloom into discs.
Why doesn't the subject get a blurry halo?
A naive blur smears the subject's colours into the background around its edge. BGVault first removes the subject from the background plate and fills that area from its surroundings, then blurs, then places the sharp subject back on top.
What is bokeh?
Bokeh is the look of out-of-focus areas. A real lens renders every out-of-focus point of light as a disc the shape of the aperture, so street lights and sparkles become soft circles. The Lens bokeh option imitates this by boosting highlights before blurring.
How do I get real background blur with a camera?
Use a wider aperture (smaller f-number), get closer to your subject, and put more distance between the subject and the background. A longer focal length helps too. The calculator on this page shows how each change affects the blur.
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