Идеально размытый градиент

Gradient Color

Fade Force

SVG

<svg
  width="512"
  height="512"
  viewBox="0 0 512 512"
  fill="none"
  xmlns="http://www.w3.org/2000/svg"
>
  <rect
    width="512"
    height="512"
    fill="url(#gaussian)"
  />

<defs>
    <radialGradient
      id="gaussian"
      cx="0"
      cy="0"
      r="1"
      gradientUnits="userSpaceOnUse"
      gradientTransform="
        translate(256 256)
        rotate(90)
        scale(256)
      "
      color-interpolation="linearRGB"
    >
      
      <stop
        offset="0.00%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="1.000"
      />

<stop
        offset="0.39%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="1.000"
      />

<stop
        offset="1.18%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.999"
      />

<stop
        offset="2.27%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.997"
      />

<stop
        offset="3.59%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.993"
      />

<stop
        offset="5.13%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.985"
      />

<stop
        offset="6.87%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.974"
      />

<stop
        offset="8.79%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.958"
      />

<stop
        offset="10.88%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.936"
      />

<stop
        offset="13.14%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.909"
      />

<stop
        offset="15.55%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.874"
      />

<stop
        offset="18.11%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.833"
      />

<stop
        offset="20.82%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.786"
      />

<stop
        offset="23.66%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.733"
      />

<stop
        offset="26.64%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.674"
      />

<stop
        offset="29.75%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.612"
      />

<stop
        offset="32.99%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.546"
      />

<stop
        offset="36.35%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.480"
      />

<stop
        offset="39.83%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.414"
      />

<stop
        offset="43.43%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.351"
      />

<stop
        offset="47.14%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.291"
      />

<stop
        offset="50.97%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.236"
      />

<stop
        offset="54.91%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.187"
      />

<stop
        offset="58.96%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.145"
      />

<stop
        offset="63.11%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.109"
      />

<stop
        offset="67.37%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.080"
      />

<stop
        offset="71.73%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.057"
      />

<stop
        offset="76.20%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.040"
      />

<stop
        offset="80.76%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.027"
      />

<stop
        offset="85.43%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.017"
      />

<stop
        offset="90.19%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.011"
      />

<stop
        offset="95.05%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.007"
      />

<stop
        offset="100.00%"
        stop-color="rgb(64, 158, 255)"
        stop-opacity="0.004"
      />
    
    </radialGradient>
  </defs>
</svg>

CSS

background-image: radial-gradient(
  closest-side,
  rgba(64, 158, 255, 0.9) 0%,
  rgba(64, 158, 255, 0.9) 0.391%,
  rgba(64, 158, 255, 0.899) 1.184%,
  rgba(64, 158, 255, 0.898) 2.265%,
  rgba(64, 158, 255, 0.895) 3.59%,
  rgba(64, 158, 255, 0.889) 5.13%,
  rgba(64, 158, 255, 0.881) 6.868%,
  rgba(64, 158, 255, 0.869) 8.789%,
  rgba(64, 158, 255, 0.853) 10.882%,
  rgba(64, 158, 255, 0.833) 13.139%,
  rgba(64, 158, 255, 0.807) 15.551%,
  rgba(64, 158, 255, 0.776) 18.113%,
  rgba(64, 158, 255, 0.741) 20.819%,
  rgba(64, 158, 255, 0.7) 23.663%,
  rgba(64, 158, 255, 0.654) 26.642%,
  rgba(64, 158, 255, 0.604) 29.751%,
  rgba(64, 158, 255, 0.552) 32.988%,
  rgba(64, 158, 255, 0.497) 36.348%,
  rgba(64, 158, 255, 0.441) 39.829%,
  rgba(64, 158, 255, 0.385) 43.428%,
  rgba(64, 158, 255, 0.331) 47.142%,
  rgba(64, 158, 255, 0.28) 50.97%,
  rgba(64, 158, 255, 0.232) 54.908%,
  rgba(64, 158, 255, 0.188) 58.956%,
  rgba(64, 158, 255, 0.15) 63.11%,
  rgba(64, 158, 255, 0.117) 67.37%,
  rgba(64, 158, 255, 0.089) 71.733%,
  rgba(64, 158, 255, 0.066) 76.198%,
  rgba(64, 158, 255, 0.048) 80.763%,
  rgba(64, 158, 255, 0.034) 85.427%,
  rgba(64, 158, 255, 0.023) 90.189%,
  rgba(64, 158, 255, 0.015) 95.047%,
  rgba(64, 158, 255, 0) 100%
)