social-metadata-hardening – Marketing & SEO skill for AI agents

Social Metadata Hardening Skill

Fix social sharing so every important URL unfurls as a rich card across all platforms.

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When to Use

• Use when shared links show missing, stale, cropped, or incorrect previews on social and chat platforms.
• Use when auditing Open Graph, Twitter/X card, image URL, alt text, or metadataBase coverage in a web app.
• Use before launch when every public page needs predictable rich previews across LinkedIn, X, Facebook, WhatsApp, Slack, Discord, and Telegram.

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Why Previews Break

| Problem | Root Cause |

|---------|-----------|

| No preview at all | Missing og:title, og:description, or og:image |

| Broken image | Relative URL (must be absolute) |

| Wrong image size | Image not 1200×630px (OG standard) |

| Plain text card | Twitter card type missing or set to summary |

| Stale preview | Platform caching old metadata |

| Metadata missing on crawl | Tags added by client-side JS (crawlers don't run JS) |

---

The Gold Standard Metadata Block

Every shareable page needs ALL of these in static HTML:

// Next.js App Router — lib/socialMetadata.js
export function buildSocialMetadata({
  title,
  description,
  path,          // '/blog/my-post'
  image,         // '/images/og/my-post.jpg' or full URL
  imageAlt,
  imageWidth = 1200,
  imageHeight = 630,
}) {
  const baseUrl = process.env.NEXT_PUBLIC_BASE_URL || 'https://www.yourdomain.com';
  
  // Always produce an absolute URL
  if (!image) throw new Error("An approved preview image is required");
  const imageUrl = new URL(image, baseUrl).href;
  const pageUrl = new URL(path, baseUrl).href;
  if (new URL(imageUrl).protocol !== "https:" || new URL(pageUrl).protocol !== "https:") {
    throw new Error("Public metadata URLs must use HTTPS");
  }
  
  // Detect MIME type from extension
  const ext = new URL(imageUrl).pathname.split('.').pop().toLowerCase();
  const mimeMap = { jpg: 'image/jpeg', jpeg: 'image/jpeg', png: 'image/png', webp: 'image/webp' };
  const imageType = mimeMap[ext] || 'image/jpeg';

  return {
    title,
    description,
    alternates: { canonical: pageUrl },
    openGraph: {
      title,
      description,
      url: pageUrl,
      type: 'website',  // use 'article' for blog posts
      images: [{
        url: imageUrl,
        secureUrl: imageUrl,   // explicit HTTPS version
        width: imageWidth,
        height: imageHeight,
        alt: imageAlt || title,
        type: imageType,
      }],
    },
    twitter: {
      card: 'summary_large_image',  // NOT 'summary' — that shows a tiny image
      title,
      description,
      images: [imageUrl],
    },
  };
}

---

Applying the Helper

Static page

// app/about/page.js
import { buildSocialMetadata } from '@/lib/socialMetadata';

export const metadata = buildSocialMetadata({
  title: 'About Us | My Site',
  description: 'Learn about our team and mission.',
  path: '/about',
  image: '/images/og/about.jpg',
  imageAlt: 'The My Site team',
});

Dynamic page (blog post, tool page)

// app/blog/[slug]/page.js
import { buildSocialMetadata } from '@/lib/socialMetadata';

export async function generateMetadata({ params }) {
  const { slug } = await params; // Compatible with async params in newer Next.js.
  const post = await getPost(slug);
  return buildSocialMetadata({
    title: `${post.title} | My Blog`,
    description: post.excerpt,
    path: `/blog/${slug}`,
    image: post.ogImage || '/images/og/default.jpg',
    imageAlt: post.title,
  });
}

Homepage (app/layout.js or app/page.js)

export const metadata = {
  metadataBase: new URL('https://www.yourdomain.com'), // REQUIRED for absolute URLs
  ...buildSocialMetadata({
    title: 'My Site — Tagline Here',
    description: 'Site-wide description.',
    path: '/',
    image: '/images/og/home.jpg',
  }),
};

> ⚠️ Set metadataBase when using relative metadata URLs. If your helper already outputs absolute canonical/OG URLs, previews can still work without it.

---

OG Image Checklist

Good OG images:

• 1200 × 630px (approximately 1.91:1; verify crop/requirements on each target platform)
• Under 8MB (Facebook limit)
• Served over HTTPS
• File name has no spaces (use hyphens)
• Format: JPEG or PNG (WebP works on most but not all crawlers)
• Accessible via GET with no authentication

# Verify your OG image is reachable and correct size
curl -sI https://www.yourdomain.com/images/og/home.jpg | grep -i "content-type\|content-length\|status"

---

Platform-Specific Notes

Facebook / Meta

• Caches aggressively — use the [Sharing Debugger](https://developers.facebook.com/tools/debug/) to force recrawl
• Minimum image: 200×200px (but use 1200×630 for quality)
• Needs: og:title, og:description, og:image, og:url

X / Twitter

• Use twitter:card = summary_large_image for full-width images
• twitter:image must be an absolute URL
• Use the [Card Validator](https://cards-dev.twitter.com/validator) to test

LinkedIn

• Caches hard — use [Post Inspector](https://www.linkedin.com/post-inspector/) to refresh
• Respects og: tags; ignores twitter: tags
• Image must be ≥1.91:1 aspect ratio

WhatsApp / Telegram

• Read OG tags on first share; cache can last hours
• Re-share after a few hours for the cache to clear naturally

Slack / Discord

• Both use OG tags; both cache
• Discord also supports og:type = article for richer embeds

---

Debugging Social Previews

1. Check raw HTML for tags

curl -s https://www.yourdomain.com/blog/my-post | grep -i "og:\|twitter:"

If tags don't appear → they're being added by JavaScript (not crawlable). Fix: move to export const metadata or generateMetadata.

2. Validate with platform tools

| Platform | Tool |

|----------|------|

| Facebook | https://developers.facebook.com/tools/debug/ |

| LinkedIn | https://www.linkedin.com/post-inspector/ |

| Twitter/X | https://cards-dev.twitter.com/validator |

| General | https://metatags.io |

3. Force cache refresh

After deploying fixes, paste the URL into each platform's debugger and click "Fetch new scrape information" (or equivalent).

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Social Metadata Checklist

• [ ] metadataBase set in root layout
• [ ] All shareable pages use shared buildSocialMetadata helper
• [ ] OG image URLs are absolute (start with https://)
• [ ] secureUrl set equal to url in OG image block
• [ ] Image is 1200×630px, under 8MB, HTTPS
• [ ] twitter:card is summary_large_image (not summary)
• [ ] Image alt text present
• [ ] Tags visible in raw HTML (not JavaScript-rendered)
• [ ] All platform debuggers show correct preview
• [ ] Cache refreshed on all platforms after deployment

Limitations

• Cannot force immediate cache refresh on every social platform; some previews may remain stale after a correct fix.
• Requires publicly reachable deployed URLs for reliable validation with platform debuggers.
• Does not replace brand, accessibility, or legal review of image text, alt text, and preview copy.