# Subdomain Finder - Certificate Transparency & DNS (`antishock/subdomain-finder-certificate-transparency`) Actor

Enumerate subdomains of any domain from public Certificate Transparency logs and resolve each to IP or CNAME. Returns live status, certificate count, first and last seen dates, issuers and wildcard flag. For attack surface management, authorised recon and vendor discovery. No API key.

- **URL**: https://apify.com/antishock/subdomain-finder-certificate-transparency.md
- **Developed by:** [Ryan Zinburg](https://apify.com/antishock) (community)
- **Categories:** Developer tools, SEO tools
- **Stats:** 2 total users, 1 monthly users, 100.0% runs succeeded, 0 bookmarks
- **User rating**: No ratings yet

## Pricing

from $1.00 / 1,000 result exporteds

This Actor is paid per event. You are not charged for the Apify platform usage, but only a fixed price for specific events.

Learn more: https://docs.apify.com/actors/running/actors-in-store.md#pay-per-event

## What's an Apify Actor?

An Actor is a serverless cloud program that runs on the Apify platform. It has two run modes.
In Batch mode, an Actor accepts a well-defined JSON input, performs an action which can take anything from a few seconds to a few hours,
and optionally produces a well-defined JSON output, datasets with results, or files in key-value store.
In Standby mode, an Actor provides a web server which can be used as a website, API, or an MCP server.

Apify vocabulary and the platform model are defined once, in the agent quickstart at https://apify.com/agents.md.

## How to integrate an Actor?

If asked about integration, you help developers integrate Actors into their projects.
You adapt to their stack and deliver integrations that are safe, well-documented, and production-ready.

Do not guess an integration path. Every one of them is in the agent quickstart at https://apify.com/agents.md: the Apify MCP server, Agent Skills with the Apify CLI, the JavaScript and Python clients, the REST API, and the account-free path for an agent with no human to sign in. It also carries the rule on stating cost before the first paid run.

For examples already wired to this Actor's own input schema, see the [API](#api) section below.

Each client library has reference documentation the quickstart does not restate: [JavaScript/TypeScript](https://docs.apify.com/api/client/js/docs.md) (`npm install apify-client`) and [Python](https://docs.apify.com/api/client/python/docs.md) (`pip install apify-client`).

# README

## Subdomain Finder - Certificate Transparency & DNS

Enumerate the **subdomains of any domain** from public Certificate Transparency logs, then resolve each one to see which are actually live. No brute forcing, no wordlists: every publicly trusted TLS certificate is logged, so the names are a matter of record.

No API key, no proxy needed.

### What you get per subdomain

| Field | Example |
|---|---|
| `subdomain` | api.example.com |
| `domain` | example.com |
| `ipAddresses` | \["93.184.216.34"] |
| `cname` | example.map.cdn.net |
| `isLive` | whether it resolves today |
| `certificateCount` | how many certificates mention it |
| `firstSeen`, `lastSeen` | earliest and latest certificate dates |
| `certificateExpired` | whether the newest certificate has lapsed |
| `issuers` | Let's Encrypt, DigiCert, ... |
| `isWildcard` | whether the entry is a wildcard name |

### Input

- **domain** - the domain to enumerate, e.g. `example.com`
- **resolveDns** - resolve each name to A records or a CNAME (on by default)
- **onlyLive** - keep only names that resolve
- **includeWildcards** - include `*.example.com` style entries
- **includeExpired** - include names whose certificates have expired (on by default, since they reveal historical infrastructure)
- **maxResults** - how many subdomains to save

### Example input

```json
{
  "domain": "example.com",
  "resolveDns": true,
  "onlyLive": true,
  "maxResults": 1000
}
```

### Use cases

- **Attack surface management** - inventory what a domain actually exposes, including hosts nobody remembers
- **Authorised penetration testing and bug bounty recon** - build the target list before scanning
- **Shadow IT discovery** - find staging, admin and vendor-hosted hosts under a corporate domain
- **Certificate hygiene audits** - spot expired certificates and unexpected issuers
- **Technology and vendor mapping** - CNAME targets reveal which SaaS platforms a company uses, which is strong B2B signal
- **M\&A technical due diligence** - see the infrastructure footprint of a target company from the outside

### Why Certificate Transparency beats brute forcing

Since 2018, browsers only trust certificates that have been logged publicly. Every HTTPS host a company has ever issued a certificate for is therefore recorded, including internal-sounding names that never appear in DNS zone transfers or wordlists. Historical entries also survive after a host is decommissioned, which is why `firstSeen` and `lastSeen` are worth keeping.

DNS resolution then separates today's live infrastructure from the historical record.

### Notes

- Large domains can have thousands of certificates. The crt.sh query is thorough rather than fast and can take some tens of seconds before results start flowing.
- `isLive` is null when `resolveDns` is off.
- A name with `isLive` false but a recent `lastSeen` is often a host behind an internal-only DNS zone, which is exactly what makes it interesting in an audit.
- Use this only on domains you own or are authorised to assess. Enumeration is passive, but what you do with the result may not be.

# Actor input Schema

## `domain` (type: `string`):

The domain to enumerate, e.g. example.com.

## `resolveDns` (type: `boolean`):

Resolve each subdomain to its A records or CNAME.

## `onlyLive` (type: `boolean`):

Keep only subdomains that currently resolve.

## `includeWildcards` (type: `boolean`):

Include wildcard entries such as \*.example.com.

## `includeExpired` (type: `boolean`):

Include names whose certificates have already expired.

## `maxResults` (type: `integer`):

How many subdomains to save.

## Actor input object example

```json
{
  "domain": "anthropic.com",
  "resolveDns": true,
  "onlyLive": false,
  "includeWildcards": false,
  "includeExpired": true,
  "maxResults": 200
}
```

# Actor output Schema

## `results` (type: `string`):

Scraped records in the default dataset.

# API

You can run this Actor programmatically using our API. Below are code examples in JavaScript, Python, and CLI, as well as the OpenAPI specification and MCP server setup.

## JavaScript example

```javascript
import { ApifyClient } from 'apify-client';

// Initialize the ApifyClient with your Apify API token
// Replace the '<YOUR_API_TOKEN>' with your token
const client = new ApifyClient({
    token: '<YOUR_API_TOKEN>',
});

// Prepare Actor input
const input = {
    "domain": "anthropic.com",
    "resolveDns": true,
    "maxResults": 200
};

// Run the Actor and wait for it to finish
const run = await client.actor("antishock/subdomain-finder-certificate-transparency").call(input);

// Fetch and print Actor results from the run's dataset (if any)
console.log('Results from dataset');
console.log(`💾 Check your data here: https://console.apify.com/storage/datasets/${run.defaultDatasetId}`);
const { items } = await client.dataset(run.defaultDatasetId).listItems();
items.forEach((item) => {
    console.dir(item);
});

// 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/js/docs

```

## Python example

```python
from apify_client import ApifyClient

# Initialize the ApifyClient with your Apify API token
# Replace '<YOUR_API_TOKEN>' with your token.
client = ApifyClient("<YOUR_API_TOKEN>")

# Prepare the Actor input
run_input = {
    "domain": "anthropic.com",
    "resolveDns": True,
    "maxResults": 200,
}

# Run the Actor and wait for it to finish
run = client.actor("antishock/subdomain-finder-certificate-transparency").call(run_input=run_input)

# Fetch and print Actor results from the run's dataset (if there are any)
print(f"💾 Check your data here: https://console.apify.com/storage/datasets/{run.default_dataset_id}")
for item in client.dataset(run.default_dataset_id).iterate_items():
    print(item)

# 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/python/docs/quick-start

```

## CLI example

```bash
echo '{
  "domain": "anthropic.com",
  "resolveDns": true,
  "maxResults": 200
}' |
apify call antishock/subdomain-finder-certificate-transparency --silent --output-dataset

```

## MCP server setup

```json
{
    "mcpServers": {
        "apify": {
            "type": "http",
            "url": "https://mcp.apify.com/?tools=fetch-actor-details,antishock/subdomain-finder-certificate-transparency"
        }
    }
}
```

The hosted server signs you in with OAuth on first connect, so no API token belongs in this config. Clients without OAuth support can send an `Authorization: Bearer <APIFY_API_TOKEN>` header instead, using a token from API & Integrations in Apify Console (https://console.apify.com/settings/integrations).

## OpenAPI specification

Download the OpenAPI definition: https://api.apify.com/v2/actors/DvdJxqd668Hto3Xzc/builds/yTmdZFnnMk8LR7ZZY/openapi.json