Simon Willison: Cloudflare 1.1.1.1 Has a CORS-Enabled DNS JSON API — Claude Built a Tool From It
Simon Willison·low signal
Willison discovered that Cloudflare's public DNS resolver (1.1.1.1, 1.1.1.2, 1.1.1.3) exposes a CORS-enabled JSON API, meaning DNS lookups can be made directly from the browser without a backend proxy. He used Claude Code to build a browser-native DNS lookup tool on top of it in a single session. This is a useful primitive for agents or browser extensions that need to resolve hostnames without server-side infrastructure.