Agentic Browser Detection
Attributed by network
From an address range Anthropic publishes for ClaudeBot / Claude-User / Claude-SearchBot — attribution, not proof
The old signal — User-Agent
claims Anthropic ClaudeBot
User-Agent contains a token for Anthropic ClaudeBot. Anyone can send any string here, so this is a hint, never a fact.
Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
The middle signal — published IP ranges
Anthropic · ClaudeBot / Claude-User / Claude-SearchBot
216.73.216.0/22 from claude.com, list dated 2026-08-18. A range names the operator, never the customer behind it, and only cloud-side operators publish one. The address is announced by AS16509 (Anthropic, PBC), as reported by the edge. A network names the landlord, not the tenant — OpenAI runs in Microsoft’s, Anthropic’s crawler in Amazon’s — so this is context, never proof. Cloudflare has verified this bot itself and files it under AI Crawler.
216.73.217.94
The new signal — Web Bot Auth
no signature
no HTTP Message Signature on this request
Everything this request carried
Every header as received, credentials removed. The client address is what the edge reported in CF-Connecting-IP; the User-Agent is verbatim.
Show all 11 request headers
accept: */*
accept-encoding: gzip, br
cf-connecting-ip: 216.73.217.94
cf-ipcountry: US
cf-ray: a36508546ef2b5b3
cf-visitor: {"scheme":"https"}
connection: Keep-Alive
host: botauth.info
user-agent: Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
x-forwarded-proto: https
x-real-ip: 216.73.217.94
Policy applied
Verdict attributed → action allow. Purpose Training (documented by the operator for this product) — established, so a purpose rule in the policy would apply. Change the mapping in the ops console.
Point something at this page
Every request to this URL is classified live. Open the ops console in a second window and watch them arrive.
node agent.js demo https://botauth.info/     # run every scenario
node agent.js verified https://botauth.info/
node agent.js spoof    https://botauth.info/