Build a Domain Authority Checker with Claude Code

Build a Domain Authority Checker web app. People search for "domain authority checker" about 80,000 times a month, plus related searches like "check domain authority", "website authority checker", "seo domain analysis". The goal is a tool that ranks for those searches and makes money.

What it should do:
Build a domain authority checker web app. Create a homepage with URL input field and 'Check Authority' button. When users enter a domain, show comprehensive metrics: domain authority score, page authority, spam score, and backlink count. Add comparison tool for multiple domains and historical tracking charts. Include competitor analysis and improvement recommendations. Show loading progress with SEO-focused animations and export report options. Use professional design with blue and green SEO-themed colors. Focus on domain analysis and metrics display first.

How to build it:
1. Read this folder first. If it is empty, set up Next.js (App Router, TypeScript, Tailwind). Write a short PLAN.md with the pages, components, any library or API you need, and what you are leaving for later. Then build.
2. Put the tool itself on the homepage so a visitor can use it within seconds, with no sign-up. Do the processing in the browser where you can, so it is fast and cheap to run. Look at how Moz, Ahrefs, SEMrush do it and make ours simpler and faster.
3. Make it rank. Use "domain authority checker" in the title tag, H1 and meta description. Under the tool, add a short how-to and an FAQ with FAQPage schema, and add a sitemap and robots.txt. Scaffold these programmatic pages from one template and a data file: /check-domain-authority-[website], /domain-analysis-for-[industry], /seo-checker-[metric].
4. Monetisation: Freemium: 5 checks/day, $15/mo unlimited + historical data. Add a pricing page and the free usage limit, and leave Stripe checkout as a clearly marked stub with the environment variables it needs.
5. Run it locally and test the main flow end to end, including edge cases like empty input and very large files. Fix what breaks, then finish with a summary of what works, what is stubbed and how to deploy it to Vercel.

Paste it into Claude Code in an empty folder. It plans first, so read PLAN.md and steer before it starts building.