I built a REST API that detects what technologies any website is running. You give it a URL, it gives you back the full stack: frameworks, CMS, CDNs, analytics, payment processors, etc.

What makes it different from BuiltWith/Wappalyzer:

- 4 detection layers running simultaneously: Wappalyzer fingerprinting (3,500+ signatures), DNS CNAME analysis (29 infrastructure signatures), TLS certificate inspection (8 issuer patterns), and custom HTTP header matching. Most tools only do one of these.

- Batch endpoint: analyze up to 10 URLs in a single request with concurrent processing.

- Compare endpoint: pass 2-10 URLs, get back shared vs unique technologies.

- CPE identifiers on every detected technology, so you can map directly to the NVD vulnerability database for security audits.

- 24-hour smart cache: cached responses return in <5ms and don't count against your quota.

Tech stack: Go, chi router, SQLite, wappalyzergo. Runs on a single Fly.io machine.

Free tier is 100 requests/month. Pro is $29.99 for 25K requests — significantly cheaper than BuiltWith ($295/mo minimum).

Try the live demo on the homepage, or check the API spec: https://detectzestack.fly.dev/openapi.yaml

Happy to answer questions about the detection approach or the architecture.