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crt.name
crt.nametool

crt.name

crt.name is a free subdomain index and API that returns every subdomain on file for a given apex domain plus first-seen dates, built by continuously parsing SAN hostnames from Certificate Transparency logs (Static CT sources like Let's Encrypt Sunlight, Geomys, Cloudflare Raio, plus legacy RFC 6962 logs like Google Argon, Sectigo, DigiCert), supplemented by Internet Archive CT replays, Common Crawl, ICANN CZDS zone files, ProjectDiscovery Chaos, HaGeZi DNS blocklists, and an active hostname prober. It offers a no-token REST API (100 req/IP/day), a Streamable HTTP MCP server exposing a single search tool for agent clients, and is the default crt source in the subfaster CLI subdomain enumerator.

TL;DR Free CT-log-backed subdomain lookup API with an MCP endpoint and default integration in the subfaster recon CLI.
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Organisations named here

  • Cloudflare Raio
  • DigiCert
  • Geomys
  • Google Argon
  • HaGeZi
  • Let's Encrypt Sunlight
  • Sectigo

Technologies named here

  • crt.name
  • Static CT
  • RFC 6962
  • Internet Archive
  • Common Crawl
  • ICANN CZDS zone files
  • ProjectDiscovery Chaos
  • HaGeZi DNS blocklists
  • crt.name prober
  • crt.name API
  • crt.name MCP
  • subfaster
  • Model Context Protocol
  • ICANN CZDS

Techniques named here

  • Certificate Transparency log parsing
  • Subdomain enumeration via known-hostname probing

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