Search the subdomain index.
crt.name
Search the subdomain index.
Give it an apex domain. You get every subdomain on file, plus the date each name first showed up.
Apex domain Search →
Free · no token · 1000 requests per IP per day
How the index is built
Live CT. The index reads every usable CT log in Chrome's and Apple's programs as entries land: Static CT (Let's Encrypt Sunlight, Geomys, Cloudflare Raio) and legacy RFC 6962 (Google Argon, Sectigo, DigiCert). It parses each certificate in memory, pulls out the SAN hostnames, then throws the rest away.
Backfill. The live feed only sees forward, so most of the depth is history: retired CT logs replayed from the Internet Archive, plus Common Crawl, ICANN CZDS zone files, ProjectDiscovery Chaos, and HaGeZi DNS blocklists.
Active probing. A prober works through common hostnames against known apexes on a loop, and anything it turns up joins the same index.
Every name is normalized by apex. The index keeps three fields, (apex, subdomain, first-seen). It holds no certificate metadata and never deletes a name.
API
GET /v1/search?apex=namecheap.com free · no token
No token. 1000 requests per IP per day. Returns one subdomain per line by default. `apex` must be an eTLD+1; use `?format=json`for JSON or `&dates=1` to include first-seen dates.
GET /v1/find?q=loginclosed betaSearch all indexed names when you know part of a subdomain.
GET /v1/top?n=100closed betaApexes ranked by how many subdomains the index holds.
GET /v1/streamclosed betaServer-sent events for newly indexed names.
Token access (higher limits and the endpoints above) is in closed beta. Paid plans are not available yet.
MCP
POST /mcp free · no token
Streamable HTTP endpoint for agent clients. Shares the free `/v1/search` budget (same counter). One tool, `search`: pass an apex, get every indexed subdomain. No token; free tier does not probe.
CLI
github.com/melvinsh/subfaster crt source · on by default
A subdomain enumerator that queries this index directly. Its `crt` source runs by default and takes no key, so `subfaster -d namecheap.com` reaches the free API on a fresh install.