Subdomain Enumeration via Certificate Transparency (crt.sh)

x402

Subdomain Enumeration via Certificate Transparency (crt.sh) is a paid API for AI agents from x402-deployer.x402-deployer.workers.dev, paid per call via x402, $0.03/call, status unknown (last checked 2026-09-14).

Enumerates subdomains for a given domain by querying Certificate Transparency logs via crt.sh, returning each subdomain with first-seen, last-seen, and certificate count.

Price / call$0.03

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StatusUnknown

How this service works

Subdomain enumeration / attack-surface mapping / DNS recon. Certificate Transparency log mining (crt.sh). All-public data. Each subdomain with first-seen, last-seen, cert count.

Output

A list of discovered subdomains for the queried domain, each with a first-seen timestamp, last-seen timestamp, and the number of certificates observed for that subdomain in CT logs.

Example use cases

Example prompt

“Can you enumerate all subdomains for example.com using certificate transparency logs and show me when each one was first and last seen?”

Technical details

Endpoint

POSThttps://x402-deployer.x402-deployer.workers.dev/subdomain-enum

When to prefer

Use this endpoint when you need passive subdomain discovery without active scanning, relying on public certificate transparency logs for comprehensive historical subdomain data including first/last seen metadata. Ideal for OSINT, attack surface mapping, and reconnaissance workflows where stealth and passivity matter.

Side effects

Domain not found in crt.sh — returns empty list
Invalid or malformed domain input — returns error
crt.sh upstream timeout or unavailability — returns upstream error
Rate limiting by crt.sh backend — may return partial results or error
Payment failure (x402) — request not processed

Input

{
  "input": {
    "body": {
      "domain": "example.com",
      "include_wildcards": false
    },
    "type": "http",
    "method": "POST",
    "bodyType": "json"
  }
}

Output

{
  "notes": "Subdomains here have appeared in TLS certificates. They may not currently resolve. Use a DNS resolver to verify liveness.",
  "domain": "example.com",
  "source": "Certificate Transparency logs via crt.sh",
  "subdomains": [
    {
      "hostname": "as207960 test intermediate - example.com",
      "last_seen": "2031-08-29T15:55:23",
      "cert_count": 2,
      "first_seen": "2021-08-31T15:55:23",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "dev.example.com",
      "last_seen": "2018-07-14T23:59:59",
      "cert_count": 1,
      "first_seen": "2016-07-14T00:00:00",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "example.com",
      "last_seen": "2033-01-24T01:21:18",
      "cert_count": 105,
      "first_seen": "2014-11-06T00:00:00",
      "distinct_issuer_count": 17
    },
    {
      "hostname": "m.example.com",
      "last_seen": "2017-07-14T23:59:59",
      "cert_count": 1,
      "first_seen": "2016-07-14T00:00:00",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "m.testexample.com",
      "last_seen": "2017-07-14T23:59:59",
      "cert_count": 1,
      "first_seen": "2016-07-14T00:00:00",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "products.example.com",
      "last_seen": "2018-07-14T23:59:59",
      "cert_count": 1,
      "first_seen": "2016-07-14T00:00:00",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "subjectname@example.com",
      "last_seen": "2011-10-01T16:32:00",
      "cert_count": 2,
      "first_seen": "2010-09-02T16:36:49",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "support.example.com",
      "last_seen": "2018-07-14T23:59:59",
      "cert_count": 1,
      "first_seen": "2016-07-14T00:00:00",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "user@example.com",
      "last_seen": "2033-01-24T01:21:18",
      "cert_count": 1,
      "first_seen": "2023-01-27T01:21:18",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "www.example.com",
      "last_seen": "2026-12-02T23:59:59",
      "cert_count": 31,
      "first_seen": "2014-11-06T00:00:00",
      "distinct_issuer_count": 8
    }
  ],
  "subdomain_count": 10,
  "cert_log_entries_examined": 69
}

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How this service works

Subdomain enumeration / attack-surface mapping / DNS recon. Certificate Transparency log mining (crt.sh). All-public data. Each subdomain with first-seen, last-seen, cert count.

Output

A list of discovered subdomains for the queried domain, each with a first-seen timestamp, last-seen timestamp, and the number of certificates observed for that subdomain in CT logs.

Technical details

Endpoint

POSThttps://x402-deployer.x402-deployer.workers.dev/subdomain-enum

When to prefer

Side effects

Domain not found in crt.sh — returns empty list
Invalid or malformed domain input — returns error
crt.sh upstream timeout or unavailability — returns upstream error
Rate limiting by crt.sh backend — may return partial results or error
Payment failure (x402) — request not processed

Input

{
  "input": {
    "body": {
      "domain": "example.com",
      "include_wildcards": false
    },
    "type": "http",
    "method": "POST",
    "bodyType": "json"
  }
}

Output

{
  "notes": "Subdomains here have appeared in TLS certificates. They may not currently resolve. Use a DNS resolver to verify liveness.",
  "domain": "example.com",
  "source": "Certificate Transparency logs via crt.sh",
  "subdomains": [
    {
      "hostname": "as207960 test intermediate - example.com",
      "last_seen": "2031-08-29T15:55:23",
      "cert_count": 2,
      "first_seen": "2021-08-31T15:55:23",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "dev.example.com",
      "last_seen": "2018-07-14T23:59:59",
      "cert_count": 1,
      "first_seen": "2016-07-14T00:00:00",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "example.com",
      "last_seen": "2033-01-24T01:21:18",
      "cert_count": 105,
      "first_seen": "2014-11-06T00:00:00",
      "distinct_issuer_count": 17
    },
    {
      "hostname": "m.example.com",
      "last_seen": "2017-07-14T23:59:59",
      "cert_count": 1,
      "first_seen": "2016-07-14T00:00:00",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "m.testexample.com",
      "last_seen": "2017-07-14T23:59:59",
      "cert_count": 1,
      "first_seen": "2016-07-14T00:00:00",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "products.example.com",
      "last_seen": "2018-07-14T23:59:59",
      "cert_count": 1,
      "first_seen": "2016-07-14T00:00:00",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "subjectname@example.com",
      "last_seen": "2011-10-01T16:32:00",
      "cert_count": 2,
      "first_seen": "2010-09-02T16:36:49",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "support.example.com",
      "last_seen": "2018-07-14T23:59:59",
      "cert_count": 1,
      "first_seen": "2016-07-14T00:00:00",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "user@example.com",
      "last_seen": "2033-01-24T01:21:18",
      "cert_count": 1,
      "first_seen": "2023-01-27T01:21:18",
      "distinct_issuer_count": 1
    },
    {
      "hostname": "www.example.com",
      "last_seen": "2026-12-02T23:59:59",
      "cert_count": 31,
      "first_seen": "2014-11-06T00:00:00",
      "distinct_issuer_count": 8
    }
  ],
  "subdomain_count": 10,
  "cert_log_entries_examined": 69
}