В html файле прописала:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta http-equiv="X-UA-Compatible" content="ie=edge" />
<link rel="stylesheet" href="svg.css" />
<title>Document</title>
</head>
<body>
<svg class="icon">
<use xlink:href="sprite.svg#facebook"></use>
</svg>
<svg class="icon">
<use xlink:href="sprite.svg#twitter"></use>
</svg>
</body>
</html>
svg файл:
<svg display="none" xmlns="http://www.w3.org/2000/svg">
<symbol id="facebook" viewBox="0 0 112.196 112.196">
<g>
<circle cx="56.098" cy="56.098" r="56.098" />
<path
style="fill:#FFFFFF;"
d="M70.201,58.294h-10.01v36.672H45.025V58.294h-7.213V45.406h7.213v-8.34
c0-5.964,2.833-15.303,15.301-15.303L71.56,21.81v12.51h-8.151c-1.337,0-3.217,0.668-3.217,3.513v7.585h11.334L70.201,58.294z"
/>
</g>
</symbol>
<symbol id="twitter" viewBox="0 0 112.197 112.197">
<g>
<circle cx="56.099" cy="56.098" r="56.098" />
<g>
<path
style="fill:#F1F2F2;"
d="M90.461,40.316c-2.404,1.066-4.99,1.787-7.702,2.109c2.769-1.659,4.894-4.284,5.897-7.417
c-2.591,1.537-5.462,2.652-8.515,3.253c-2.446-2.605-5.931-4.233-9.79-4.233c-7.404,0-13.409,6.005-13.409,13.409
c0,1.051,0.119,2.074,0.349,3.056c-11.144-0.559-21.025-5.897-27.639-14.012c-1.154,1.98-1.816,4.285-1.816,6.742
c0,4.651,2.369,8.757,5.965,11.161c-2.197-0.069-4.266-0.672-6.073-1.679c-0.001,0.057-0.001,0.114-0.001,0.17
c0,6.497,4.624,11.916,10.757,13.147c-1.124,0.308-2.311,0.471-3.532,0.471c-0.866,0-1.705-0.083-2.523-0.239
c1.706,5.326,6.657,9.203,12.526,9.312c-4.59,3.597-10.371,5.74-16.655,5.74c-1.08,0-2.15-0.063-3.197-0.188
c5.931,3.806,12.981,6.025,20.553,6.025c24.664,0,38.152-20.432,38.152-38.153c0-0.581-0.013-1.16-0.039-1.734
C86.391,45.366,88.664,43.005,90.461,40.316L90.461,40.316z"
/>
</g>
</g>
</symbol>
</svg>
svg и html находятся в одной папке. Если вставлять svg непосредственно в html иконки отображаются.
