changedetection.io/changedetectionio/content_fetchers/res/favicon-fetcher.js

(async () => {
  // Define the function inside the IIFE for console testing
  window.getFaviconAsBlob = async function() {
    const links = Array.from(document.querySelectorAll(
      'link[rel~="apple-touch-icon"], link[rel~="icon"]'
    ));

    const icons = links.map(link => {
      const sizesStr = link.getAttribute('sizes');
      let size = 0;
      if (sizesStr) {
        const [w] = sizesStr.split('x').map(Number);
        if (!isNaN(w)) size = w;
      } else {
        size = 16;
      }
      return {
        size,
        rel: link.getAttribute('rel'),
        href: link.href,
        hasSizes: !!sizesStr
      };
    });

    // If no icons found, add fallback favicon.ico
    if (icons.length === 0) {
      icons.push({
        size: 16,
        rel: 'icon',
        href: '/favicon.ico',
        hasSizes: false
      });
    }

    // sort preference: highest resolution first, then apple-touch-icon, then regular icons
    icons.sort((a, b) => {
      // First priority: actual size (highest first)
      if (a.size !== b.size) {
        return b.size - a.size;
      }
      
      // Second priority: apple-touch-icon over regular icon
      const isAppleA = /apple-touch-icon/.test(a.rel);
      const isAppleB = /apple-touch-icon/.test(b.rel);
      if (isAppleA && !isAppleB) return -1;
      if (!isAppleA && isAppleB) return 1;
      
      // Third priority: icons with no size attribute (fallback icons) last
      const hasNoSizeA = !a.hasSizes;
      const hasNoSizeB = !b.hasSizes;
      if (hasNoSizeA && !hasNoSizeB) return 1;
      if (!hasNoSizeA && hasNoSizeB) return -1;
      
      return 0;
    });

    const timeoutMs = 2000;

    for (const icon of icons) {
      try {
        const controller = new AbortController();
        const timeout = setTimeout(() => controller.abort(), timeoutMs);

        const resp = await fetch(icon.href, {
          signal: controller.signal,
          redirect: 'follow'
        });

        clearTimeout(timeout);

        if (!resp.ok) {
          continue;
        }

        const blob = await resp.blob();

        // Convert blob to base64
        const reader = new FileReader();
        return await new Promise(resolve => {
          reader.onloadend = () => {
            resolve({
              url: icon.href,
              base64: reader.result.split(",")[1]
            });
          };
          reader.readAsDataURL(blob);
        });

      } catch (e) {
        continue;
      }
    }

    // nothing found
    return null;
  };

  // Auto-execute and return result for page.evaluate()
  return await window.getFaviconAsBlob();
})();