SEO Checklist for Custom Web Applications (Next.js, SaaS & Beyond)

SEO Checklist for Custom Web Applications

Custom web applications aren't like static sites or CMS-driven blogs. They're built on frameworks like Next.js, React, and modern SaaS stacks, which introduce unique SEO challenges: dynamic routing, hydration issues, Server Component architecture, and structured data complexity.

If you're building or running a Next.js app, SaaS product, or enterprise web portal, this checklist gives you the step-by-step actions you need in 2026 to stay visible in both traditional search engines and AI-driven experiences like Google AI Overviews, Perplexity, and ChatGPT. These strategies align with the broader SEO trends shaping 2026.

For AI-specific optimization strategies, see our companion post: AI Search Optimization Guide.

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1. Core Web Vitals (2026 Benchmarks)

Google continues to use Core Web Vitals as ranking signals. In 2026, poor INP scores above 300ms have caused 31% ranking drops — particularly on mobile. Your app must meet these thresholds:

Metric	Good	Needs Improvement	Poor
LCP (Largest Contentful Paint)	< 2.5s	2.5s – 4.0s	> 4.0s
INP (Interaction to Next Paint)	< 200ms	200ms – 500ms	> 500ms
CLS (Cumulative Layout Shift)	< 0.1	0.1 – 0.25	> 0.25

How to Optimize in Next.js 15

LCP optimization:

• Use the next/image component with AVIF/WEBP formats and priority for above-the-fold images
• Preload fonts with <link rel="preload" as="font" crossOrigin="anonymous">
• Use streaming with loading.tsx to show content faster
• Enable Partial Prerendering (PPR) to serve static shells immediately

INP optimization:

• Minimize JavaScript execution on the main thread
• Use React.lazy() and Suspense for code splitting
• Offload heavy computations to Web Workers
• Audit third-party scripts — analytics, chat widgets, and ad scripts are common offenders

CLS optimization:

• Set explicit width and height on images and videos
• Use CSS aspect-ratio for responsive containers
• Avoid dynamically injected content above the fold
• Preload fonts to prevent FOIT/FOUT layout shifts

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2. Next.js 15 App Router: Technical SEO Foundations

Server Components (Default)

Next.js 15's App Router uses Server Components by default — a major SEO advantage. Search engines and AI crawlers receive fully rendered HTML, not JavaScript that needs execution.

• SEO-critical pages (pricing, features, docs, blog) should always render on the server
• Client Components ('use client') should be reserved for interactive elements only
• Server Components reduce bundle size, improving LCP and INP

Partial Prerendering (PPR)

PPR is the most impactful Next.js 15 feature for SEO. It combines static and dynamic rendering in the same route:

• Static shell (headings, meta tags, core content) renders at build time — instant delivery
• Dynamic holes (personalized content, user-specific data) stream in asynchronously
• Crawlers see the complete static content immediately
• Enable in next.config.ts: cacheComponents: true

Metadata API

Centralize all meta tags using the Metadata API:

// app/blog/[slug]/page.tsx
import type { Metadata } from 'next'

export async function generateMetadata({ params }): Promise<Metadata> {
  const post = await getPost(params.slug)
  return {
    title: post.seoTitle,
    description: post.seoDescription,
    alternates: {
      canonical: `https://www.example.com/blog/${params.slug}`,
    },
    openGraph: {
      title: post.title,
      description: post.description,
      type: 'article',
      publishedTime: post.date,
    },
  }
}

Routing Best Practices

• Use SSR or SSG for all indexable pages — never rely on client-only rendering for SEO content
• Implement generateStaticParams() for static generation of dynamic routes
• Use loading.tsx for streaming — gives crawlers content faster than full SSR
• Set dynamicParams = false for known routes to prevent 404s on invalid slugs

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3. XML Sitemaps & Indexing

Sitemap Configuration

Use the built-in App Router convention or next-sitemap:

// app/sitemap.ts
import type { MetadataRoute } from 'next'

export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
  const posts = await getAllPosts()
  return [
    { url: 'https://www.example.com', lastModified: new Date(), priority: 1.0 },
    { url: 'https://www.example.com/blog', lastModified: new Date(), priority: 0.8 },
    ...posts.map(post => ({
      url: `https://www.example.com/blog/${post.slug}`,
      lastModified: new Date(post.date),
      priority: 0.7,
    })),
  ]
}

Indexing Checklist

• Generate sitemap with canonical URLs only (no www vs non-www duplicates)
• Include lastModified dates (YYYY-MM-DD format)
• Submit sitemap in Google Search Console
• Verify no duplicate or orphan URLs in sitemap
• Check "Indexed, not submitted in sitemap" errors in Search Console

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4. Robots.txt & AI Crawler Configuration

Configure robots.txt to allow both traditional and AI crawlers:

// app/robots.ts
import type { MetadataRoute } from 'next'

export default function robots(): MetadataRoute.Robots {
  return {
    rules: [
      {
        userAgent: '*',
        allow: '/',
        disallow: ['/api/', '/admin/', '/_next/'],
      },
      {
        userAgent: ['GPTBot', 'PerplexityBot', 'ClaudeBot', 'Applebot-Extended'],
        allow: '/',
      },
    ],
    sitemap: 'https://www.example.com/sitemap.xml',
  }
}

2026 note: Google no longer uses Google-Extended to control AI Overview inclusion. AI Overviews are now a core search feature controlled by standard Googlebot access.

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5. Schema Markup Essentials

Schema helps both Google and AI systems understand your content. For apps and SaaS sites, implement:

Schema Type	Use Case	AI Impact
Organization	Company identity, brand queries	Knowledge panel, entity recognition
SoftwareApplication	SaaS products, web tools	Product rich results
FAQPage	Support docs, FAQ sections	AI Overview citations, People Also Ask
Article / BlogPosting	Blog content, guides	AI citation source
HowTo	Step-by-step tutorials	Featured snippets, AI extraction
BreadcrumbList	Navigation hierarchy	Rich results, crawl clarity

Example (SoftwareApplication with pricing):

{
  "@context": "https://schema.org",
  "@type": "SoftwareApplication",
  "name": "QuickETL",
  "operatingSystem": "Web",
  "applicationCategory": "BusinessApplication",
  "offers": {
    "@type": "AggregateOffer",
    "priceCurrency": "USD",
    "lowPrice": "0",
    "highPrice": "499",
    "offerCount": "3"
  },
  "aggregateRating": {
    "@type": "AggregateRating",
    "ratingValue": "4.7",
    "reviewCount": "156"
  }
}

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6. Internal Linking Strategy

• Hub-spoke model: Link blog posts to their primary service page (e.g., SEO posts → /seo)
• Descriptive anchor text: "Next.js SEO checklist" instead of "click here"
• Topic clusters:
  • SEO for Web Apps: This checklist → AI Search Optimization Guide → On-Page SEO Checklist
  • Software Development: SaaS Architecture → API Integration Guide

Strong linking between technical posts and service pages improves both SEO authority and conversion. If you're worried about conversion loss, see: Is Your Website Costing You Customers?.

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7. Security & Accessibility

Security Headers (Next.js)

// next.config.ts headers()
{ key: 'X-Content-Type-Options', value: 'nosniff' },
{ key: 'X-Frame-Options', value: 'DENY' },
{ key: 'Referrer-Policy', value: 'origin-when-cross-origin' },
{ key: 'Strict-Transport-Security', value: 'max-age=63072000; includeSubDomains; preload' },

Accessibility Checklist

• All images have descriptive alt text
• Color contrast meets WCAG 2.2 AA standards (4.5:1 for normal text)
• Keyboard navigation works for all interactive elements
• Form labels are properly associated with inputs
• ARIA landmarks used for major page sections

Accessibility improvements directly correlate with better SEO signals — reduced bounce rate, improved engagement, and better crawlability.

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8. AI Search Discoverability

AI Overviews now appear in 60% of Google searches. Your web app must be AI-discoverable:

• Write citation-worthy content — Clear definitions, specific data, direct answers
• Use structured data — FAQPage, HowTo, and Article schema help AI parse your content
• Make headings scannable — AI extracts information by heading hierarchy
• Monitor AI bot activity — Track GPTBot, PerplexityBot, and ClaudeBot in server logs
• Ensure HTML rendering — Some AI bots can't execute JavaScript. Critical content should be in the initial HTML (Server Components handle this automatically)

For the advanced playbook, see AI Search Optimization Guide.

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9. Measurement & Tracking

Essential Tools

Tool	What to Track	Frequency
Google Search Console	Indexing, query impressions, AI Overview visibility	Weekly
GA4	Engagement, conversions, scroll depth	Weekly
Core Web Vitals Reports	CrUX data, field performance	Monthly
Server logs	AI bot crawl frequency and coverage	Monthly
Schema Validator	Structured data compliance	After changes

Optimization Cadence

• Weekly: Ship updates and track search performance changes
• Monthly: Audit Core Web Vitals, review AI search visibility, check indexing coverage
• Quarterly: Refresh high-value pages, conduct comprehensive SEO audits, and update structured data

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Taking Action

SEO for custom web applications in 2026 requires a dual focus:

1. Technical foundations — Core Web Vitals with INP, Server Components, clean sitemaps, and schema markup
2. AI discoverability — Structured content, citation-worthy answers, and AI crawler access

By following this checklist, your custom web app will rank higher in traditional search, earn citations in AI Overviews, and convert visitors more effectively.

Need expert help? Our SEO Optimization Services combine technical audits with AI search optimization to help businesses improve rankings and capture more qualified leads. We specialize in Next.js and modern web application SEO.