Next.js SEO Optimization

Comprehensive SEO guide for Next.js App Router applications.

Quick SEO Audit

Run this checklist for any Next.js project:

1. Check robots.txt: curl https://your-site.com/robots.txt
2. Check sitemap: curl https://your-site.com/sitemap.xml
3. Check metadata: View page source, search for <title> and <meta name="description">
4. Check JSON-LD: View page source, search for application/ld+json
5. Check Core Web Vitals: Use PageSpeed Insights (pagespeed.web.dev) and the Search Console CWV report for field data — Lighthouse is lab-only and can't measure INP

Essential Files

app/layout.tsx - Root Metadata

import type { Metadata, Viewport } from 'next';

// Viewport must be a separate export — `themeColor`, `colorScheme`, and
// `viewport` inside the `metadata` object are deprecated (since v14: still
// emitted with a warning today, not guaranteed to stay).
export const viewport: Viewport = {
  width: 'device-width',
  initialScale: 1,
  maximumScale: 5,
  userScalable: true,
  themeColor: [
    { media: '(prefers-color-scheme: light)', color: '#ffffff' },
    { media: '(prefers-color-scheme: dark)', color: '#0a0a0a' },
  ],
};

export const metadata: Metadata = {
  metadataBase: new URL('https://your-site.com'),
  title: {
    default: 'Site Title - Main Keyword',
    template: '%s | Site Name',
  },
  // ~150-160 chars is a guideline, not a limit — Google truncates per device/query
  description: 'Compelling description with target keywords',
  // No `keywords` field: Google ignores the keywords meta tag entirely
  openGraph: {
    type: 'website',
    locale: 'en_US',
    url: 'https://your-site.com',
    siteName: 'Site Name',
    title: 'Site Title',
    description: 'Description for social sharing',
    images: [{ url: '/og-image.png', width: 1200, height: 630, alt: 'Site preview' }],
  },
  twitter: {
    card: 'summary_large_image',
    title: 'Site Title',
    description: 'Description for Twitter',
    images: ['/og-image.png'],
  },
  alternates: {
    canonical: '/',
  },
  robots: {
    index: true,
    follow: true,
  },
};

app/sitemap.ts - Dynamic Sitemap

import type { MetadataRoute } from 'next';

export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
  const baseUrl = 'https://your-site.com';
  const posts = await getPosts(); // your CMS/DB

  return [
    {
      url: baseUrl,
      images: [`${baseUrl}/og-image.png`], // Image Sitemap entry
    },
    { url: `${baseUrl}/about` },
    ...posts.map((post) => ({
      url: `${baseUrl}/blog/${post.slug}`,
      lastModified: post.updatedAt, // real content timestamp
    })),
  ];
}

lastModified must reflect the content's actual last change (CMS updatedAt, file mtime, git commit date) — Google uses lastmod only when it's consistently accurate, and new Date() on every build marks everything "just changed", which teaches Google to ignore it. Skip changeFrequency and priority: Google ignores both.

app/robots.ts - Robots Configuration

import type { MetadataRoute } from 'next';

export default function robots(): MetadataRoute.Robots {
  const baseUrl = 'https://your-site.com';

  return {
    rules: [
      {
        userAgent: '*',
        allow: '/',
        disallow: ['/api/', '/admin/'],
        // Do NOT disallow /_next/ — crawlers need render-critical CSS/JS
        // Do NOT add bot-specific rules (Googlebot, Bingbot) unless overriding wildcard —
        // and if you do, repeat all disallows: named groups don't inherit `*` rules
        // (RFC 9309 §2.2.1; Google never merges a specific group with `*`)
      },
    ],
    sitemap: `${baseUrl}/sitemap.xml`,
  };
}

host was omitted intentionally — it's a non-standard directive Google ignores. Use canonical URLs / 301s to declare the preferred host instead. See references/sitemap-robots.md.

app/manifest.ts - Web App Manifest

Same MetadataRoute family as sitemap/robots, placed at the root of app/. Not an SEO requirement — a PWA-completeness nicety with no ranking effect; skip it unless the site is (or may become) a PWA. Full example in references/metadata-api.md.

OG / Twitter Images

Three ways to set social images — prefer the file conventions over hand-syncing URLs in the metadata object:

1. External URL in metadata (the openGraph.images / twitter.images examples above) — fine for externally hosted images.
2. Static file convention (recommended default): drop opengraph-image.(png|jpg|gif) and/or twitter-image.* into a route segment (app/opengraph-image.png for the root, app/blog/opengraph-image.png for /blog). Next.js auto-emits og:image/twitter:image + :type/:width/:height. A deeper, more specific image overrides one above it. Add alt text with a sibling opengraph-image.alt.txt. Build fails if the file exceeds 8 MB (OG) / 5 MB (Twitter).
3. Dynamic generation with ImageResponse (per-page/per-post images): an opengraph-image.tsx in the route segment exporting alt, size, contentType and a default Image({ params }) (params is a Promise in v16) that returns new ImageResponse(<jsx/>, { ...size }). Renders via Satori — flexbox only, no display: grid; statically optimized at build time unless it reads request-time data. Full example, fonts, generateImageMetadata and the favicon/icon.tsx/apple-icon conventions: references/metadata-api.md.

Key Principles

Cache Components & SEO

With cacheComponents: true in next.config.ts (the v16 top-level flag that unifies the old experimental.dynamicIO/ppr/useCache), use the "use cache" directive for SEO-critical server components:

// app/(home)/sections/hero-section.tsx
import { cacheLife, cacheTag } from "next/cache";

export async function HeroSection() {
  "use cache";
  cacheLife("hours");   // SEO content that changes a few times/day; see profiles below
  cacheTag("hero");     // Invalidate via updateTag("hero") in a Server Action

  const data = await fetchData();
  return <div>{/* SEO-visible content */}</div>;
}

Built-in cacheLife profiles (stale / revalidate / expire): seconds (30s/1s/1m), minutes (5m/1m/1h), hours (5m/1h/1d), days (5m/1d/1w), weeks (5m/1w/30d), max (5m/30d/1y), and the implicit default (5m/15m/never). For SEO pages pick by how often content changes — days for blog/docs, max for legal/marketing. (minutes revalidates every 1 min — too aggressive for most SEO content.)

Key rules:

• "use cache" must be the first statement in the function body (or at the top of the file for file-level caching)
• No cookies()/headers()/searchParams inside a plain "use cache" scope — good for SEO, since indexable content should be request-agnostic. ("use cache: private" does allow them, but is never prerendered, so it never lands in the static SEO shell.)
• Invalidate with updateTag("hero") inside a Server Action (read-your-writes; it throws outside one), or revalidateTag("hero", "max") from a Route Handler / webhook (pass the profile — the one-argument form is legacy behaviour) — prefer these over export const revalidate
• Very short cache profiles can change what Next.js includes in the prerendered shell. Do not infer that behavior from revalidate alone: choose a profile from the documented freshness requirements and verify the installed Next.js version's next build output. Prefer hours/days/max for SEO-critical content unless the product genuinely needs fresher data
• Sitemaps and metadata are static by default — only add "use cache" (+ cacheTag) if they fetch CMS/dynamic data you want to invalidate on publish

Rendering Strategy for SEO

Strategy	Use When	SEO Impact
"use cache"	Server components with periodic data	Best - cached HTML, fast TTFB
SSG (Static)	Content rarely changes	Best - pre-rendered HTML
SSR	Dynamic content per request	Great - server-rendered
CSR	Dashboards, authenticated areas	Poor - avoid for SEO pages

Core Web Vitals Targets

Metric	Target	Impact
LCP (Largest Contentful Paint)	< 2.5s	Loading speed
INP (Interaction to Next Paint)	< 200ms	Interactivity
CLS (Cumulative Layout Shift)	< 0.1	Visual stability

• Measured on field data, not lab. Google ranks on the 75th percentile of real users (Chrome UX Report, 28-day rolling window, mobile/desktop separate). A URL group passes only when ≥75% of visits hit "Good" on all three. Use PageSpeed Insights and the Search Console CWV report for the real signal — Lighthouse is lab-only and cannot measure INP.
• INP replaced FID as a Core Web Vital on 2024-03-12; FID is deprecated. INP is the most commonly failed metric — prioritize it.
• Page experience is a tiebreaker, not a standalone ranking system (Google de-emphasized it). Good CWV won't rescue thin content; content relevance and quality come first. Treat CWV as baseline UX hygiene.
• Myths to ignore: 2026 SEO blogs falsely claim "LCP was lowered to 2.0s" and invent an "Engagement Reliability" metric. Neither exists in any Google/web.dev source — the LCP and CLS thresholds are unchanged since 2021, and INP's 200 ms has been fixed since it became a Core Web Vital in 2024.

Ranking Signals Beyond Technical SEO

Metadata + CWV alone don't drive rankings. Keep these in mind (out of scope for this skill, but pointers):

• Helpful content is part of core ranking (since 2024-03), evaluated continuously — not an episodic penalty.
• E-E-A-T (Experience, Expertise, Authoritativeness, Trust): cite real authors/credentials and first-hand experience, especially on YMYL pages.
• Mobile-first indexing is complete (since 2024-07): Google indexes the mobile rendering only. Ensure the mobile view has the same content, metadata, and structured data as desktop; never block mobile resources. (Mostly automatic with Next.js responsive design.)

References

• Metadata API — references/metadata-api.md: read when writing generateMetadata, OG/icon files, ImageResponse, the manifest, or when streaming metadata / htmlLimitedBots is in play
• Sitemap & Robots — references/sitemap-robots.md: read for generateSitemaps, image/video sitemaps, multi-group robots rules, static robots.txt/sitemap.xml files
• JSON-LD Structured Data — references/json-ld.md: read before adding any schema type; has the supported/deprecated rich-result list and the @graph pattern
• AI Search (GEO/AEO) & AI Crawlers — references/ai-search.md: read when deciding robots rules for GPTBot/OAI-SearchBot/ClaudeBot etc., or when asked about llms.txt or AI Overviews
• SEO Audit Checklist — references/checklist.md: read when asked to audit a site end to end
• Troubleshooting — references/troubleshooting.md: read when a page is missing from Google, stuck in "Discovered/Crawled – currently not indexed", or indexes fine but never hydrates

Common Mistakes to Avoid

1. Mixing next-seo with Metadata API - Use only Metadata API in App Router
2. Missing canonical URLs - Set a self-referencing alternates.canonical when duplicate/parameterized URLs are a risk; it's a hint, not a requirement — Google may pick its own canonical
3. Using CSR for SEO pages - Use SSG/SSR for indexable content
4. Blocking /_next/ in robots.txt - Crawlers need render-critical CSS/JS; never disallow /_next/
5. Missing metadataBase - Required for relative URLs in metadata
6. Viewport in metadata - Must be a separate export
7. Mixing metadata object and generateMetadata - Use one or the other in the same route segment
8. Duplicating icons in metadata + file conventions - Prefer favicon.ico/icon.*/opengraph-image.* file conventions; they auto-emit tags and override the metadata object
9. Blanket-blocking AI crawlers - GPTBot disallow: / blocks training but leaves you in AI search; don't accidentally block citation bots (OAI-SearchBot, PerplexityBot). See references/ai-search.md
10. Adding the keywords meta tag for Google - Google ignores it entirely (no indexing or ranking effect); it's noise, not a signal
11. Assuming named robots.txt groups inherit * rules - Per RFC 9309 §2.2.1 the * group applies only when no group matches, and Google never merges a specific group with *. A { userAgent: 'OAI-SearchBot', allow: '/' } group drops the wildcard's /api///admin/ disallows — repeat them in every named group
12. Trusting browser view for bot metadata - PPR + streaming metadata has served bots pages with no <title>/canonical (vercel/next.js #95406 — check its status on your version), and the browser view never shows it. Confirm production HTML with a bot User-Agent: curl -A "Googlebot" https://your-site.com | grep -E '<title>|canonical'
13. Assuming a route that indexes well also works - A PPR route (◐ in the build output) can serve perfect SEO HTML while none of its <Suspense> boundaries hydrate on a direct load. Load the route directly in a browser and interact with it; the observation and the check are in references/troubleshooting.md.

Quick Fixes

Add noindex to a page

export const metadata: Metadata = {
  robots: {
    index: false,
    follow: false,
  },
};

Dynamic metadata per page

type Props = { params: Promise<{ id: string }> };

export async function generateMetadata({ params }: Props): Promise<Metadata> {
  const { id } = await params;            // params is a Promise in current Next.js
  const product = await getProduct(id);
  return {
    title: product.name,
    description: product.description,
  };
}

Canonical for dynamic routes

type Props = { params: Promise<{ slug: string }> };

export async function generateMetadata({ params }: Props): Promise<Metadata> {
  const { slug } = await params;
  return {
    alternates: {
      canonical: `/products/${slug}`,
    },
  };
}