blur-clip-stacking-context-001.html

<!doctype html>
<title>CSS Test: Blurs are correctly clipped by an overflow: hidden ancestor</title>
<link rel="author" href="mailto:[email protected]" title="Emilio Cobos Álvarez">
<link rel="help" href="https://drafts.fxtf.org/filter-effects/#funcdef-filter-blur">
<link rel="help" href="https://drafts.csswg.org/css-overflow-3/#valdef-overflow-hidden">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1459065">
<link rel="match" href="blur-clip-stacking-context-ref.html">
<style>
  #cover, #clip, #blur {
    width: 100px;
    height: 100px;
  }

  #cover, #clip {
    position: absolute;
    top: 10px;
    left: 10px;
  }

  #cover {
    background: green;
  }

  #clip {
    overflow: hidden;
    background: red;
  }

  #blur {
    background: blue;
    filter: blur(20px);
  }
</style>
<div id="clip"><div id="blur"></div></div>
<div id="cover"></div>

chromium/third_party/blink/web_tests/external/wpt/css/filter-effects/blur-clip-stacking-context-001.html