Just shipped: a free tool that asks ChatGPT if it can actually fetch your site - Hosting checker

I just launched Hosting Checker on my GEO/SEO product (GEOlikeaPro), and the thing I'm most excited about is the architecture, not the marketing.

The problem: every "AI crawler audit" tool I've seen does the same useless thing — they spoof a User-Agent header (`User-Agent: GPTBot`) from their server and check whether the response is 200. That's a meaningless test. Real bot blocks are by IP range, not UA. Hostinger shared plans, Cloudflare's default-on AI bot block (since July 2025), Imperva, Sucuri, Akamai — they all key off the source IP. If you fetch with User-Agent: GPTBot from a Hetzner box, you're not GPTBot, and the host doesn't treat you as such. The test passes. The real GPTBot still gets walled.

The fix: stop spoofing, ask the AI itself.

Hosting Checker takes a URL and, in parallel:

- Hits OpenAI's gpt-4o-search-preview with a prompt: "fetch this URL and tell me the title, h1, and first 200 chars." Whatever ChatGPT actually fetches from OpenAI's IPs, that's ground truth.

- Same for Perplexity (`sonar-pro`).

- DNS-resolves the host, looks up the ASN via Team Cymru DoH, fingerprints known-problematic ASNs.

- Inspects response headers (`cf-mitigated`, x-sucuri-id, x-iinfo, etc.) for vendor signatures.

- Parses robots.txt for AI-bot disallows.

Stack: single Cloudflare Worker (everything inlined into one worker.js), Supabase for auth, KV for caching + rate limits + units. The whole multi-layer probe runs in ~5 seconds.

Abuse hardening: SSRF block (private IPs / link-local / non-default ports rejected pre-DNS and post-DNS resolution), per-user-per-domain rate limit (5/hr), per-domain-global rate limit (30/hr), 30-min KV result cache (cache hits cost 0 units).

Pricing: free tier 50 units/month (~16 scans). Paid tiers add Perplexity probe and higher caps. BYOK makes it free.

The thing I want to know from you: what other "silent infrastructure block" patterns should I fingerprint? Right now I detect the major bot-protection vendors and a handful of named hosts. There's a long tail I'm probably missing.

Tool: https://geolikeapro.com/tool (Hosting Checker tab under Standards)