What is an image blur filter?

A blur filter softens a picture by mixing every pixel with its neighbors. A gaussian blur, the kind used here, gives close neighbors more weight than distant ones, so the result looks like an out of focus lens rather than a smeared copy. It turns a photo into a soft background for a slide, a website header, or a phone wallpaper, makes text on top of a busy picture easier to read, and hides the details of a screenshot while keeping its layout recognizable.

Tool description

Open an image and drag the radius. A small radius takes the edge off fine details, a large one leaves only soft patches of color. The preview updates as you drag, the comparison slider shows the original next to the result, and the download keeps the image's full size as PNG, JPG, or WebP.

Features

  • Gaussian blur with a single radius setting
  • Colors mix the way light does, so bright spots spread naturally and edges between colors don't turn muddy
  • Transparent images keep clean, soft edges
  • Runs in your browser, so the image never leaves your device

How it works

The radius is the standard deviation of the gaussian, the same measure CSS blur() uses. The blur mixes colors as amounts of light rather than as the numbers stored in the file: fine black and white stripes blur to the gray that half the light makes, which is lighter than the dull mid gray a quick blur gives. Past the edges of the image the edge pixels repeat, so the borders don't darken, and transparent pixels don't bleed their hidden color into the picture.

Tips

  • For a background behind text, pick a radius where shapes are still recognizable but nothing draws the eye.
  • Blurred images compress very well, so a JPG or WebP download is often much smaller than the original.
  • To hide sensitive text for good, use a large radius. Light blurs of large text can sometimes still be read.