How to Blur Background Image in CSS – The Ultimate Guide

Blurring a background image is a powerful design technique that enhances readability and visual focus on foreground content. Whether you’re designing a login page, a card layout, or a hero section, applying a blur effect can create a clean, modern aesthetic. In this tutorial, we’ll walk you through how to blur a background image using pure CSS.

Table of Contents

🖼️ Why Blur a Background Image?

Blurring background images helps in:

Highlighting foreground text or elements.
Creating a soft, elegant visual effect.
Improving user experience and readability.

🔧 Method 1: Blurring the Entire Background Image

The simplest way to blur a background image is by applying the filter: blur() property directly to the image or a pseudo-element behind the main content.

✅ Example using a `<div>` with background image:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Blur Background Image</title>
  <style>
    body, html {
      height: 100%;
      margin: 0;
    }

    .blur-bg {
      background-image: url('your-image.jpg');
      background-size: cover;
      background-position: center;
      height: 100vh;
      filter: blur(8px);
    }
  </style>
</head>
<body>

  <div class="blur-bg"></div>

</body>
</html>

⚠️ Caveat:

The blur affects everything inside the .blur-bg container, so this approach works best when the image is in its own separate layer.

💡 Method 2: Blurred Background Behind Clear Foreground Content

To keep content sharp while only blurring the background, you can layer two elements: a blurred background layer and a clear foreground content layer.

✅ Example:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Blurred Background with Clear Content</title>
  <style>
    body, html {
      height: 100%;
      margin: 0;
    }

    .background {
      background-image: url('your-image.jpg');
      background-size: cover;
      background-position: center;
      filter: blur(8px);
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      z-index: -1;
    }

    .content {
      position: relative;
      z-index: 1;
      color: white;
      text-align: center;
      padding-top: 200px;
      font-size: 2rem;
    }
  </style>
</head>
<body>

  <div class="background"></div>

  <div class="content">
    <h1>Welcome to Our Website</h1>
    <p>This content stays sharp while the background is beautifully blurred.</p>
  </div>

</body>
</html>

🧪 Tips for Better Results

Use high-resolution background images to avoid pixelation after blurring.
Use semi-transparent overlays to enhance contrast: .overlay { background-color: rgba(0, 0, 0, 0.3); }
Keep filter: blur(px) values between 5px and 15px for subtle, readable effects.

🧾 Conclusion

Blurring background images with CSS is a modern design technique that enhances visual appeal and readability without JavaScript or heavy libraries. By using CSS properties like filter: blur() and positioning, you can create professional, layered UI effects with minimal code.

Need more visual effects? Try combining blur() with other filters like brightness(), grayscale(), or even CSS animations for dynamic experiences.