Build an SSL Certificate Checker with Claude Code

Build an SSL Certificate Checker web app. People search for "ssl certificate checker" about 5,100 times a month, plus related searches like "ssl checker tool", "certificate validator", "ssl test online". The goal is a tool that ranks for those searches and makes money.

What it should do:
Create an SSL certificate checker with domain input and instant validation. Show certificate details (issuer, expiry, encryption), security grade, and chain verification. Include mobile/desktop compatibility checks and security recommendations. Add bulk domain checking and email alerts for expiring certificates. Focus on getting basic SSL validation working 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 SSL Labs, SSL Checker, DigiCert SSL Inspector do it and make ours simpler and faster.
3. Make it rank. Use "ssl certificate 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: /ssl-checker-[domain-extension], /check-ssl-[certificate-type], /ssl-validator-[platform].
4. Monetisation: Freemium: 10 checks/day, $8/mo unlimited + monitoring. 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.