This pattern shows how to build a dark and light theme adaptive favicon with SVG.
Full article · Video on YouTube · Source on Github
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 447 428" width="400" height="400">
<style>
.favicon-stroke {
stroke-width: 8px;
stroke: #8929ff;
}
#skull-outline { fill: white }
#eyes-and-nose,
#hat-outline { fill: #8929ff }
#hat-fill,
#hat-bill { fill: #e662e6 }
@media (prefers-color-scheme: dark) {
.favicon-stroke { stroke: #343a40 }
#skull-outline { fill: #adb5bd }
#hat-outline { fill: #343a40 }
#eyes-and-nose { fill: #343a40 }
}
</style>
<g id="skull">
<path id="skull-outline" class="favicon-stroke" stroke-linejoin="round" d="M19.62 188.39A166.62 166.62 0 0 1 186.24 21.77c115.25 0 166.61 74.59 166.61 166.62 0 1.83-.08 3.64-.13 5.46h.13s.68 175.09.68 178.65c0 30.11-16.26 41.67-36.32 41.67-12.7 0-35.22-3.93-36.22-32.69h-.2c-1 28.76-16.81 32.69-36.22 32.69-18 0-32.87-6.78-35.77-32.53-2.9 25.75-17.8 32.53-35.8 32.53-20.06 0-36.32-11.56-36.32-41.67 0-2.48.36-24.88.36-24.88A166.68 166.68 0 0 1 19.62 188.39Z" />
<path id="eyes-and-nose" d="M180.77 205.76c0 23.64 12.84 42.81 28.68 42.81s28.68-19.17 28.68-42.81-12.84-42.82-28.68-42.82-28.68 19.17-28.68 42.82M275 205.76c0 23.64 12.84 42.81 28.68 42.81s28.68-19.17 28.68-42.81-12.84-42.82-28.68-42.82S275 182.11 275 205.76M264.51 276.85s-29.26 43.53-20.12 49.23c7.07 4.41 20.49-16.71 20.49-16.71s12.82 22.58 16.76 20c16.24-10.71-17.13-52.5-17.13-52.5"/>
<path id="jawline" class="favicon-stroke" fill="none" stroke-linecap="round" d="M114.92 284.33c22.54-1 22 7 22 62.48" />
</g>
<g id="hat">
<path id="hat-fill" d="m36.27 118.44 2-5.41c.37-1 9.25-24.14 33-47.53 21.83-21.56 60.88-47.26 122.91-47.26C258 18.24 294.8 44 314.46 65.65c21.38 23.52 27.49 46.82 27.74 47.8l1.27 5Z"/>
<path id="hat-outline" d="M194.17 22.24c120.68 0 144.15 92.2 144.15 92.2H42.05s34.67-92.2 152.12-92.2m0-8c-27.9 0-53.65 5.07-76.52 15.08a162.3 162.3 0 0 0-49.21 33.33c-24.31 24-33.5 48-33.88 49l-4.07 10.82h318.13l-2.54-10c-.26-1-6.62-25.26-28.66-49.51a140.29 140.29 0 0 0-46.52-33.6c-22.25-10-48.06-15.12-76.73-15.12"/>
<path id="hat-bill" class="favicon-stroke" stroke-linecap="square" d="M350.7 117.76c69.17 0 112.9-106.93 57.6-106.93-81 0-95.18 74.6-198.47 106.93M80.32 117.86h267.53"/>
</g>
</svg>