# Next.js SEO checklist for the App Router: 14 technical checks with code and curl > A technical Next.js SEO checklist for the App Router: server HTML, metadata, canonicals, status codes under streaming, redirects, robots.ts, sitemaps and JSON-LD. Source: https://seofix.ai/blog/nextjs-seo-checklist Published: 2026-11-15 Updated: 2026-11-02 Author: SEOFix Team Category: Technical SEO Tags: Technical SEO, Guides Length: 1,690 words, 8 min read Next.js SEO in the App Router comes down to a short list: the content is in the HTML the server sends, every page has its own title, description and absolute canonical from `generateMetadata`, missing pages return a real `404`, moved pages return a single `308`, `robots.ts` and `sitemap.ts` serve the right thing on the right host, and streaming doesn't undo any of it. The App Router gets most of this right by default. The failures are in the defaults that interact: `loading.tsx` with `notFound()`, slow `generateMetadata` with canonicals, Proxy with `/robots.txt`. Below are the 14 checks we'd run on any App Router site, each with the code and a curl command to verify it. The behaviours marked "tested" were checked on a Next.js 16.4.2 production build on 2 November 2026. Each check links to a longer post where there is one. ## 1. The content is in the server HTML Server Components render on the server, so their output is in the response. Client components that fetch in `useEffect` render an empty shell first. Google renders JavaScript, but it does so later, and most AI crawlers don't run it at all ([Do AI crawlers render JavaScript?](https://seofix.ai/blog/do-ai-crawlers-render-javascript)). ```bash # words of real content in the raw HTML (before any JavaScript) curl -s https://example.com/blog/hello-world | sed 's/<[^>]*>/ /g' | wc -w # does a phrase from the article body appear? curl -s https://example.com/blog/hello-world | grep -c 'a sentence from the article' ``` If the phrase isn't there, find the client component that loads it and move the fetch into a Server Component parent. SEOFix's on-page checks read this same raw HTML, and its render sample compares it with the rendered page ([JavaScript rendering](https://seofix.ai/help/javascript-rendering)). Testing JavaScript crawlability covers comparing raw and rendered HTML in more depth. ## 2. Every page sets its own title and description Put a template in the root layout and set `title` and `description` per page: ```typescript // app/layout.tsx export const metadata: Metadata = { metadataBase: new URL('https://example.com'), title: { default: 'Example', template: '%s ยท Example' }, description: 'What the site does, in one sentence.', } ``` ```typescript // app/blog/[slug]/page.tsx export async function generateMetadata({ params }: Props): Promise { const post = await getPost((await params).slug) return { title: post.title, description: post.excerpt } } ``` Two inheritance rules from the [generateMetadata reference](https://nextjs.org/docs/app/api-reference/functions/generate-metadata) cause most duplicate-title reports. A page that doesn't set `title` uses its parent's, so every page you forgot gets the site name as its title. And metadata merges shallowly: a page that sets `openGraph: { title }` loses the layout's `openGraph.images` and `openGraph.description` entirely. Spread the shared parts into each page. ```bash curl -s https://example.com/blog/hello-world | grep -o -E '[^<]*|]*>' ``` ## 3. One absolute, self-referencing canonical per page Set `metadataBase` once, then `alternates: { canonical: '/path' }` per page, built from the route and not the request, so `?utm_source=` never ends up in it. Don't put a fixed canonical in a layout: every child page without its own inherits it, and in our test a layout's `canonical: '/'` made a child page canonicalise to the home page. Paginated pages keep `?page=n` in their canonical, as Google's [canonicalization guide](https://developers.google.com/search/docs/crawling-indexing/consolidate-duplicate-urls) and pagination guide ask. The details, including what `'./'` resolves to and the trailing-slash trap, are in Next.js canonical tag. ## 4. Metadata lands in the head for Googlebot Since Next.js 15.2, `generateMetadata` can stream: its tags are "appended to the `` tag" for browsers and for Googlebot, while bots on the `htmlLimitedBots` list (Bingbot, social previews) get them in `` ([docs](https://nextjs.org/docs/app/api-reference/functions/generate-metadata)). Tested: with a `loading.tsx` in the route, or a page that renders without waiting for the data `generateMetadata` needs, the canonical and title sat in the body for a Googlebot user agent. Google's canonicalization guide says the canonical "is only accepted if it appears in the ``." ```bash curl -s -A 'Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)' https://example.com/blog/hello-world \ | awk '/^\/head>/{print "---- end of head ----"} /rel="canonical"/{print "canonical here"}' RS='<' ``` If the canonical prints after "end of head", either let the page await the same cached data before rendering, or add Googlebot to `htmlLimitedBots`. Both are explained in the canonical post. ## 5. Missing pages return 404, not 200 `notFound()` sends a `404` only before the response starts streaming. Tested: a `loading.tsx` in the route or any parent folder, a `` boundary above the check, or a `notFound()` that only runs in `generateMetadata` all produced `200` with a `noindex` meta tag. The [notFound docs](https://nextjs.org/docs/app/api-reference/functions/not-found) confirm the mechanism: once streaming has started, the response "keeps its `200` status." ```bash for p in /blog/zz-missing /products/zz-missing; do curl -s -o /dev/null -w "%{http_code} $p\n" "https://example.com$p" done ``` Every dynamic template should print `404`. The fixes (await the lookup first, share it with `generateMetadata`, or check in Proxy) are in Next.js 404 status code. ## 6. Outages return 5xx, not 404 The reverse bug is worse. A data function that returns `null` when the database times out, followed by `if (!post) notFound()`, tells Google that real pages are gone. Google [removes indexed URLs](https://developers.google.com/crawling/docs/troubleshooting/http-status-codes) that return `4xx`, while `5xx` only slows its crawling. Distinguish "not found" from "couldn't check": ```typescript async function getPost(slug: string) { const res = await fetch(`${API}/posts/${slug}`) if (res.status === 404) notFound() if (!res.ok) throw new Error(`posts API ${res.status}`) // error.tsx, 500 return res.json() } ``` ## 7. Permanent moves are a single 308 `permanent: true` in `next.config` and `permanentRedirect()` send `308`; `redirect()` and `NextResponse.redirect()` without a status send `307` (tested). Google treats `308` like `301`. Write destinations in their final form, because Next.js's own trailing-slash redirect adds a hop to a destination like `/new/` (tested: two `308`s in a row). ```bash curl -s -o /dev/null -L -w '%{num_redirects} hops, final %{http_code}: %{url_effective}\n' https://example.com/old-path ``` More, including redirects that turn into a meta refresh after streaming, in Next.js redirects. ## 8. One URL shape: trailing slash, host, protocol By default Next.js redirects `/about/` to `/about`; `trailingSlash: true` reverses it ([docs](https://nextjs.org/docs/app/api-reference/config/next-config-js/trailingSlash)). Pick one and make canonicals, sitemap URLs and internal links match it. Do `http` to `https` and `www` to apex at the CDN or reverse proxy, in one hop. ```bash for u in http://example.com/about https://www.example.com/about https://example.com/about/; do curl -s -o /dev/null -L -w "%{num_redirects} hops -> %{url_effective}\n" "$u" done ``` All three should end at the same URL in one hop. ## 9. robots.ts serves the right rules on the right host `app/robots.ts` "is cached by default unless it uses a Request-time API or dynamic config option" ([docs](https://nextjs.org/docs/app/api-reference/file-conventions/metadata/robots)). Tested: an environment check inside it ran at build time, and a build made without the production variable served `Disallow: /` in production. Decide by the request's host with `headers()`, which makes the route dynamic. ```bash curl -s https://example.com/robots.txt curl -s https://staging.example.com/robots.txt ``` Code and the staging setup are in Next.js robots.txt. ## 10. Proxy leaves robots.txt and the sitemap alone Proxy without a `matcher` "runs on **every request**" ([Proxy docs](https://nextjs.org/docs/app/api-reference/file-conventions/proxy)). An auth or locale Proxy that redirects `/robots.txt` or `/sitemap.xml` breaks both files for crawlers. List the paths Proxy needs, or exclude the metadata files: ```typescript export const config = { matcher: ['/((?!api|_next/static|_next/image|favicon\\.ico|robots\\.txt|sitemap|llms\\.txt).*)'], } ``` ```bash for f in robots.txt sitemap.xml; do curl -s -o /dev/null -w "%{http_code} %{content_type} %{redirect_url} $f\n" "https://example.com/$f" done ``` Both should answer `200` with no redirect URL. ## 11. The sitemap lists only indexable 200 URLs, with real dates `app/sitemap.ts` is cached the same way as robots.ts, so a database-driven sitemap can freeze at build time. Add `revalidate`, filter out noindex and redirected records, and use a content timestamp for `lastModified`, not `new Date()`. All of it, plus `generateSitemaps` for large sites, is in Next.js sitemap. ```bash curl -s https://example.com/sitemap.xml | grep -c '' curl -s https://example.com/sitemap.xml | grep -o '[^<]*' | sort | uniq -c | sort -rn | head -3 ``` If the top `lastmod` value covers almost every URL, the dates aren't real. ## 12. Noindex where it belongs, and nowhere else Use the `robots` metadata field for pages that should stay crawlable but out of results (internal search, thin filter combinations, login): ```typescript export const metadata: Metadata = { robots: { index: false, follow: true } } ``` For PDFs and other files, send `X-Robots-Tag` with the `headers` option (tested: the rule below added the header to `/files/a.pdf` and not to `/files/b.txt`) in `next.config` ([headers docs](https://nextjs.org/docs/app/api-reference/config/next-config-js/headers)): ```typescript async headers() { return [{ source: '/files/:path*.pdf', headers: [{ key: 'X-Robots-Tag', value: 'noindex' }] }] } ``` Don't also disallow those URLs in robots.txt: Google's [robots meta docs](https://developers.google.com/search/docs/crawling-indexing/robots-meta-tag) say the directives "can be read and followed only if crawlers are allowed to access the pages." And check that no layout sets `robots: { index: false }` for a whole section by accident: ```bash curl -s https://example.com/pricing | grep -o ']*>' curl -sI https://example.com/pricing | grep -i x-robots-tag ``` Both should print nothing (or `index, follow`) on pages you want in search. Noindex vs disallow has the decision table. ## 13. Links are real links, images have alt text Google "can only crawl your link if it's an `` HTML element with an `href` attribute" ([Google](https://developers.google.com/search/docs/crawling-indexing/links-crawlable)). `next/link` "extends the HTML `` element" ([Link docs](https://nextjs.org/docs/app/api-reference/components/link)), so `` is fine. A `