Check out example codes for "css blur background image only". It will help you in understanding the concepts better.

Code Example 1

.image {
  /* The image used */
  background-image: url("photographer.jpg");

  /* Add the blur effect */
  filter: blur(8px);
  -webkit-filter: blur(8px);

  /* Full height */
  height: 100%;

  /* Center and scale the image nicely */
  background-position: center;
  background-repeat: no-repeat;
  background-size: cover;
}

Code Example 2

/* Answer to "blur behind element css" */

/*
	This blurs everything behind the element it's applied to
*/

backdrop-filter: blur(10px);

Code Example 3

// best workaround is two images layered... (one on left is on top)
background-image: url(opaque_blurred.png), url(regular_bakground_img.jpg);
// BAM! that right there is worth at least a buck donation ;-)

Code Example 4

/* Answer to: "blur effect css" */

/*
  Learn how to create a blurry background image with CSS using a
  tutorial made by W3Schools, here's the link:
  https://www.w3schools.com/howto/howto_css_blurred_background.asp
*/

body, html {
  height: 100%;
}

* {
  box-sizing: border-box;
}

.bg-image {
  /* The image used */
  background-image: url("photographer.jpg");

  /* Add the blur effect */
  filter: blur(8px);
  -webkit-filter: blur(8px);

  /* Full height */
  height: 100%;

  /* Center and scale the image nicely */
  background-position: center;
  background-repeat: no-repeat;
  background-size: cover;
}

/* Position text in the middle of the page/image */
.bg-text {
  background-color: rgb(0,0,0); /* Fallback color */
  background-color: rgba(0,0,0, 0.4); /* Black w/opacity/see-through */
  color: white;
  font-weight: bold;
  border: 3px solid #f1f1f1;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  z-index: 2;
  width: 80%;
  padding: 20px;
  text-align: center;
}

Code Example 5

background: rgba(255,255,255,0.5);
backdrop-filter: blur(5px);

Learn ReactJs, React Native from akashmittal.com