DEV3 Free DNS, SSL and Security Header Checker — Source Code (Next.js + MongoDB)

Source code of the DEV3 DNS, SSL and Security Header Checker, a domain checker that runs DNS lookups, reads the TLS certificate chain and grades HTTP security headers, all from one API call.

Free download: sign in to any DEV3 account and click Download ZIP. Try it live: https://dev3.tech/tools/dns-ssl-header-checker shows the finished tool running.

What is in the download

• Route handlers and pages for the Next.js App Router
• The service layer, Mongoose models and the UI components, in a dev3-tools/ folder that cannot clash with your own files
• README.md (install, environment, customise), .env.example and an MIT LICENSE

What the code does

• A, AAAA, CNAME, MX, NS, TXT, CAA and SOA lookups with timeouts via node:dns
• tls.connect to port 443 of the validated public IP only, chain, SAN and expiry days
• Security header grading with fix hints
• Host and redirect validation through the SSRF guard

Tech stack

Next.js 15 (App Router), React 19, TypeScript, Mongoose on MongoDB, Tailwind CSS 4.

Install and customise

The How to install and How to use tabs list the steps. In short: copy the module into a Next.js app, install the listed packages, add the MongoDB connection string and run it.

Good to know

• This is server code: you need a MongoDB database and your own hosting.
• One host and one request; results depend on the resolver of the server.