Next.js SEO Metadata Tutorial: generateMetadata to JSON-LD

export function buildCanonical(locale: SiteLocale, path = ""): string {
  const url = `${BASE_URL}/${locale}${path}`;
  return url.endsWith("/") ? url : `${url}/`;
}

export function buildLanguageAlternates(path = ""): Record<string, string> {
  return {
    en: buildCanonical("en", path),
    id: buildCanonical("id", path),
    "x-default": buildCanonical("en", path),
  };
}

Every URL on the site is built here, and nowhere else. buildCanonical always returns an absolute address with a trailing slash, matching the site's trailingSlash setting. buildLanguageAlternates returns en, id and x-default, and x-default points at English.

  return {
    // Absolute: post titles are written to sit inside Google's ~63-character
    // budget, and the root layout's "%s | Matthews Wong" template would add 16
    // more and truncate every one of them. That template used to be suppressed
    // by the plain-string title in blog/layout.tsx, which no longer sets one.
    title: { absolute: title },
    description,
    keywords: blog.keywords,
    alternates: {
      canonical,
      languages: buildLanguageAlternates(routePath),
    },

A post's metadata. The canonical is the page's own URL in its own language, and the language map comes from the same helper. The title is absolute because it is already written to fit about 63 characters; the root template would add a brand tail and get it truncated.

    title: {
      default: seo.title,
      // Kept as a safety net for any route that sets a plain-string title.
      // Every page with length-budgeted copy sets `title: { absolute }`, which
      // bypasses this so the brand tail is not appended twice.
      template: "%s | Matthews Wong",
    },

The root layout keeps a template, but its own comment calls it a safety net. The site's convention is that every page sets title.absolute with its brand tail already included, so the template rarely fires.

    // Absolute: the title already carries the brand tail, so the root
    // layout's "%s | Matthews Wong" template would append a second one.
    title: { absolute: seo.title },

This layout sets only an absolute title. In Next.js 15.5.7 the template passed to child segments comes from the nearest segment that declares one, so everything under /education loses the root template. The thesis page below it says so in a comment and sets its own absolute title.

        url: buildCanonical(locale, path),
        lastModified: routeLastModified[path],
        priority: route.priority,
        changeFrequency: route.changeFrequency,
        images: routeImages[path],
        videos: routeVideos[path]?.(locale),
        alternates: {
          languages: buildLanguageAlternates(path),
        },

One sitemap entry. The URL, the language alternates and the last-modified date all come from data, and the alternates reuse the helper from lib/seo.ts, so the sitemap and the head tags cannot disagree. Google ignores the priority and changeFrequency lines here; they are harmless but do no work.

const ALLOW = ["/", "/api/v1/"];
const DISALLOW = ["/private/", "/admin/", "/api/"];

export default function robots(): MetadataRoute.Robots {
  return {
    rules: [
      { userAgent: "*", allow: ALLOW, disallow: DISALLOW },
      ...AI_CRAWLERS.map((userAgent) => ({
        userAgent,
        allow: ALLOW,
        disallow: DISALLOW,
      })),
    ],
    host: BASE_URL,
    sitemap: `${BASE_URL}/sitemap.xml`,
  };
}

robots.ts builds its rules from two shared arrays, so the generic crawler and every named AI crawler get the same policy. The sitemap line points crawlers at the one registry of real pages.

      {articleSchema && (
        <script
          type="application/ld+json"
          dangerouslySetInnerHTML={{ __html: JSON.stringify(articleSchema) }}
        />
      )}

JSON-LD from a server component, as the docs recommend: a native script tag fed by plain data. What I would change: the docs sanitise the output with a replace of the less-than character, and this code does not. The data here is ours, but the habit costs one call.