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HTML

              
                <body>
  <div class="wrapper">
    <header>
      <div class="container">
        <h1 class="logo">
          <a href="/">CSS Background Image Blur without blurry edges</a>
        </h1>
        <p>Trying to get rid of the blurry edges when using filter:blur() on a background image.</p>
      </div><!--.container-->
    </header>

    <main>
      <article class="container">
        <p>
          Using <code>filter: blur(2px)</code> on a background image that is set to be the cover image of the whole page, can result in ugly edges. 
        </p>
        <p>I tried to get rid of them with various techniques.</p>

        <h2>Negative absolute positioning</h2>
        <p>The parent wrapper has <code>overflow: hidden</code> so anything inside it even when over <code>100%</code> should not make the viewport wider.</p>
        <p>Using negative <code>top|bottom|left|right: -1%</code> values and increased the <code>width|height: 102%</code> moved the background image to the right position. But the blurry edges still were there. Damn.</p>
        
        <h2>Negative margin</h2>
        <p>Setting a negative <code>margin: -2%</code> had no effect either.</p>
        
        <h2>Clipping the image</h2>
        <p>Some people did suggest using <code>clip:rect()</code>. What does work when using an <code>img</code> with known dimensions. But unfortunately <code>clip:rect()</code> does not support percentage values, which we would need to crop a full size background image with unknown width/height.</p>
        
        <h2>Solution</h2>
        <p>Enough talking about what didn't work - here is what did:</p>
        <p>Simply scaling the background image to <code>110%</code> by using <code>transform: scale(1.1)</code> makes the background image heigher and wider. Blurry edges gone. Perfect.</p>
        
        <p><strong>But don't forget the vendor prefixes for <code>transform: scale</code></strong></p>
        
      </article>
    </main>
    
  </div><!--.wrapper-->
</body>
              
            
!

CSS

              
                @import url(//fonts.googleapis.com/css?family=Open+Sans:400,700,800,300);

$color-primary: #34495E;
$color-black: #333;
$color-grey: #ECF0F1;


*,*:before,*:after{
  box-sizing: border-box;
}

// .group is the new clearfix
.group:after {
  content: "";
  display: table;
  clear: both;
}

html{
  position: absolute;
  z-index: 1;
  height: 100%;
  width: 100%;
  overflow: hidden;
  
  &:before{
    content: '';
    display: block;
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    background: #fff url('http://newevolutiondesigns.com/images/freebies/city-wallpaper-11.jpg') center center fixed no-repeat;
    background-size: cover;
    filter: blur(2px);
    // this does the trick
    transform: scale(1.1);
  }
}

body{
  position: relative;
  overflow: auto; // needed because html has overflow: hidden
  margin: 0 auto;
  padding: 0;
  width: 100%;
  height: 100%;
  background: #E2E2E2;
  color: #333;
  font-size: 100%;
  font-family: 'Open Sans','Helvetica Neue',Helvetica, sans-serif;
  line-height: 1.45;
}

a{
  text-decoration: none;
  color: $color-primary;
  transition: all 150ms ease-in-out;

  &:hover{
    color: darken($color-primary,8%);
  }
}

header{
  margin: 0;
  padding: 1rem 0;
  background: rgba($color-primary,.8);
  
  .logo{
    display: block;
    margin: 0 1rem;
    padding: 0;
    text-align: center;
    
    a{
      display: block;
      font-size: 1.3rem;
      color: #fff;
    }
  }
  p{
    display: block;
    margin: 0;
    padding: 0;
    text-align: center;
    font-size: 0.9rem;
    color: #ccc;
  }
}

.container{
  display: block;
  position: relative;
  margin: 0 auto;
  width: 90%;
  max-width: 900px;
}

main{
  margin: 3rem 0;
  padding: 0;
}
article{
  border-radius: 2px;
  background: rgba($color-grey,.9);
  padding: .5rem 1.5rem;
  
  
  h2{
    font-size: 1.1rem;
    letter-spacing: -1px;
    margin: 1rem 0;
    padding: 0;
  }
  
  p{
    padding: 0;
    margin: 1rem 0;
  }
  
  code{
    display: inline-block;
    font-size: .8em;
    font-weight: normal;
    background: rgba($color-primary,.2);

    border-radius: 3px;
    padding: 2px 3px 1px;
  }
}

h1,h2,h3,h4,h5,h6{
  margin: 0;
  padding: 0;
}
              
            
!

JS

              
                
              
            
!
999px

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