# Certificate Transparency Logs Subdomain & SSL/TLS Asset Finder (`apex-b2b-data/ct-logs-subdomain-certificate-finder`) Actor

Discover all active and historical subdomains, staging environments, API gateways, and SSL/TLS certificates for any target domain via Certificate Transparency (crt.sh) logs with concurrent live DNS A/CNAME verification.

- **URL**: https://apify.com/apex-b2b-data/ct-logs-subdomain-certificate-finder.md
- **Developed by:** [George Barnes](https://apify.com/apex-b2b-data) (community)
- **Categories:** Developer tools, Automation, SEO tools
- **Security:** Limited permissions
- **Stats:** 2 total users, 1 monthly users, 100.0% runs succeeded, 0 bookmarks
- **User rating**: No ratings yet

## Pricing

from $1.05 / 1,000 results

This Actor is paid per event. You are not charged for the Apify platform usage, but only a fixed price for specific events.
Since this Actor supports Apify Store discounts, the price gets lower the higher subscription plan you have.

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

## Certificate Transparency Logs Subdomain & SSL/TLS Asset Finder

[![Apify Actor](https://img.shields.io/badge/Apify-Actor-orange?logo=apify)](https://apify.com)
[![Pricing](https://img.shields.io/badge/Pricing-$1.50%20/%201K%20Assets-blue)](#pricing--pay-per-event)
[![Zero Proxies Required](https://img.shields.io/badge/Proxies-Zero%20Required-success)](#)
[![Python 3.12](https://img.shields.io/badge/Python-3.12-brightgreen)](#)

Discover all public, hidden, staging, and historical subdomains, developer environments, and API endpoints for any target domain. Powered by public **Certificate Transparency (CT) logs** (`crt.sh`) combined with **concurrent live DNS A and CNAME resolution**, this Actor gives penetration testers, cybersecurity analysts, B2B lead generation specialists, and DevOps engineers a comprehensive attack surface and infrastructure inventory in seconds.

***

### ⚡ Why Use Certificate Transparency for Subdomain Discovery?

Whenever a Certificate Authority (CA) like Let's Encrypt, DigiCert, Sectigo, or Amazon issues an SSL/TLS certificate for a domain or subdomain, cryptographic logs are publicly published to append-only Certificate Transparency logs.

Unlike active brute-force DNS scanners that query wordlists and trigger firewall blocks, CT log discovery:

1. **Finds Unindexed & Staging Assets:** Discovers subdomains before search engines or web crawlers can even detect them (e.g. `jira.corp.domain.com`, `api-v2.staging.domain.com`, `admin-portal.domain.com`).
2. **Zero Residential Proxy Costs:** Queries open public transparency logs directly without triggering rate limits or requiring expensive proxy pools.
3. **Historical Asset Footprint:** Surfaces decommissioned or unmaintained hostnames alongside active servers.
4. **Instant Live DNS Verification:** Evaluates each candidate host with concurrent IPv4 (`A`) and alias (`CNAME`) lookups to distinguish active servers from dormant DNS records.

***

### 🥊 Competitive Advantage

| Feature | `ct-logs-subdomain-certificate-finder` | SecurityTrails | Shodan / Censys | Manual crt.sh Web UI |
| :--- | :--- | :--- | :--- | :--- |
| **Pricing Model** | **$1.50 / 1,000 assets (Pay-Per-Event)** | $99 – $499 / mo subscription | $69 – $300 / mo | Free, but no API & slow |
| **Live DNS A/CNAME Resolution** | ✅ **Built-in Concurrent DNS** | ⚠️ Partial (Paid tier) | ❌ Port scan focus | ❌ None (raw text only) |
| **Wildcard Host Cleaning** | ✅ **Automatic (\*.domain -> host)** | ⚠️ Manual config | ❌ No | ❌ Raw multiline SANs |
| **Deduplication by Freshness** | ✅ **Keeps newest certificate** | ❌ None | ❌ None | ❌ 100+ duplicates per host |
| **Certificate Validity Window** | ✅ **not_before, not_after, is_expired** | ⚠️ Basic | ✅ Yes | ⚠️ Unformatted |
| **Subdomain Depth Tagging** | ✅ **Automatic (0=apex, 1=sub, 2=nested)** | ❌ No | ❌ No | ❌ No |
| **API Keys & Setup** | ✅ **Zero keys required** | ❌ API key required | ❌ API key required | ❌ No API |
| **Export Formats** | ✅ **JSON, CSV, Excel, XML, HTML, API** | ⚠️ JSON/CSV | ⚠️ JSON | ❌ Web page copy-paste |

***

### 💰 Pricing — Pay-Per-Event

Pay only for the subdomain certificate records you successfully discover and enrich. Zero recurring subscription commitments:

| Discovery Volume | Price (USD) | Effective Rate | Best For |
| :--- | :--- | :--- | :--- |
| **100 Subdomains** | **$0.15** | $0.0015 / asset | Single domain attack surface check |
| **1,000 Subdomains** | **$1.50** | $0.0015 / asset | Mid-size enterprise asset inventory |
| **10,000 Subdomains** | **$15.00** | $0.0015 / asset | Multi-domain B2B infrastructure scan |
| **50,000 Subdomains** | **$75.00** | $0.0015 / asset | Continuous attack surface management |

***

### 🎯 Copy-Paste Input Playbooks

#### Playbook 1: Default Discovery (Single Domain Quick Audit)

Discovers up to 25 unique subdomains for `apify.com`, resolving live IP addresses and CNAME aliases:

```json
{
  "domains": ["apify.com"],
  "resolveDns": true,
  "maxSubdomainsPerDomain": 25,
  "activeOnly": false,
  "excludeWildcards": true
}
```

#### Playbook 2: Active Attack Surface Recon (Security & Bug Bounty)

Filters out all decommissioned or inactive records, returning only live hosts with resolvable IPv4 addresses or CNAMEs:

```json
{
  "domains": ["github.com"],
  "resolveDns": true,
  "maxSubdomainsPerDomain": 100,
  "activeOnly": true,
  "excludeWildcards": true,
  "maxItems": 100
}
```

#### Playbook 3: Multi-Domain Enterprise Portfolio Inventory

Scans multiple brand domains in a single automated batch run:

```json
{
  "domains": [
    "stripe.com",
    "shopify.com",
    "cloudflare.com"
  ],
  "resolveDns": true,
  "maxSubdomainsPerDomain": 50,
  "activeOnly": false,
  "timeoutSec": 45,
  "maxConcurrency": 25,
  "maxItems": 150
}
```

***

### ⚙️ Input Parameters Reference

| Parameter | Type | Default | Description |
| :--- | :--- | :--- | :--- |
| `domains` | `Array<string>` | `["apify.com"]` | List of target apex or parent domains to query across CT logs. |
| `resolveDns` | `boolean` | `true` | Concurrently query DNS A and CNAME records to verify live host activity. |
| `maxSubdomainsPerDomain` | `integer` | `25` | Maximum number of unique subdomains to discover per root domain. |
| `activeOnly` | `boolean` | `false` | When `true`, filters out inactive or NXDOMAIN subdomains. |
| `excludeWildcards` | `boolean` | `true` | Strips `*.` prefixes from SANs to extract concrete hostnames. |
| `timeoutSec` | `integer` | `30` | Request timeout in seconds for Certificate Transparency API queries. |
| `maxConcurrency` | `integer` | `20` | Thread pool size for asynchronous DNS resolution. |
| `maxItems` | `integer` | `100` | Maximum total records to return across the entire run. |

***

### 📊 Sample Output Record

Every item pushed to the Apify dataset contains 100% of the overview transformation fields plus extended intelligence attributes:

```json
{
  "domain": "apify.com",
  "subdomain": "blog.apify.com",
  "is_dns_active": true,
  "ip_addresses": [
    "151.101.131.7",
    "151.101.195.7",
    "151.101.3.7",
    "151.101.67.7"
  ],
  "cname_records": [
    "apify.ghost.io",
    "ghost.map.fastly.net"
  ],
  "cert_issuer": "C=US, O=Let's Encrypt, CN=YR1",
  "cert_not_before": "2026-10-03T10:08:23",
  "cert_not_after": "2027-01-01T10:08:22",
  "discovery_source": "crt.sh",
  "discovered_at": "2026-11-04T00:19:45Z",
  "is_expired": false,
  "subdomain_depth": 1,
  "cert_id": 29632949918,
  "logged_at": null,
  "is_wildcard": false
}
```

***

### 💻 Developer Integration

#### Python (Apify Client SDK)

```python
from apify_client import ApifyClient

client = ApifyClient("YOUR_APIFY_API_TOKEN")

run_input = {
    "domains": ["apify.com", "openai.com"],
    "resolveDns": True,
    "maxSubdomainsPerDomain": 50,
    "activeOnly": True,
}

## Start the Actor run and wait for completion
run = client.actor("your-username/ct-logs-subdomain-certificate-finder").call(run_input=run_input)

## Fetch dataset items
for item in client.dataset(run["defaultDatasetId"]).iterate_items():
    print(f"[{item['subdomain']}] Active: {item['is_dns_active']} | IPs: {item['ip_addresses']} | CNAME: {item['cname_records']}")
```

#### JavaScript / Node.js

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

const client = new ApifyClient({ token: 'YOUR_APIFY_API_TOKEN' });

const run = await client.actor('your-username/ct-logs-subdomain-certificate-finder').call({
    domains: ['apify.com'],
    resolveDns: true,
    activeOnly: true,
    maxSubdomainsPerDomain: 25,
});

const { items } = await client.dataset(run.defaultDatasetId).listItems();
console.log(`Discovered ${items.length} active subdomains:`);
items.forEach(i => console.log(`${i.subdomain} -> ${i.ip_addresses.join(', ')}`));
```

#### cURL / REST API

```bash
curl -X POST "https://api.apify.com/v2/acts/your-username~ct-logs-subdomain-certificate-finder/runs?token=YOUR_APIFY_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "domains": ["apify.com"],
    "resolveDns": true,
    "maxSubdomainsPerDomain": 25
  }'
```

#### Claude Desktop / Model Context Protocol (MCP)

Add this Actor as an automated tool in your `claude_desktop_config.json`:

```json
{
  "mcpServers": {
    "apify": {
      "command": "npx",
      "args": ["-y", "@apify/mcp-server"],
      "env": {
        "APIFY_TOKEN": "YOUR_APIFY_API_TOKEN"
      }
    }
  }
}
```

***

### 🛡️ License & Disclaimers

This Actor gathers publicly published Certificate Transparency log data in compliance with RFC 6962 and performs standard DNS resolution queries. Use responsibly for legitimate security auditing, attack surface management, and technical intelligence gathering.

# Actor input Schema

## `domains` (type: `array`):

List of apex or parent domains to query across public Certificate Transparency logs (e.g. \["apify.com", "github.com"]).

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

Perform concurrent DNS A and CNAME record queries to verify which discovered subdomains are actively online and resolve to live IPs.

## `maxSubdomainsPerDomain` (type: `integer`):

Maximum number of unique subdomains to discover and process per root domain.

## `activeOnly` (type: `boolean`):

Only output subdomains that resolve to at least one active IPv4 address or CNAME alias (excludes dormant or decommissioned hosts).

## `excludeWildcards` (type: `boolean`):

Strip wildcard prefixes (\*.) from certificate Common Names and Subject Alternative Names to discover concrete hostnames.

## `timeoutSec` (type: `integer`):

HTTP request timeout in seconds when querying public Certificate Transparency endpoints.

## `maxConcurrency` (type: `integer`):

Number of concurrent worker threads for asynchronous DNS resolution.

## `maxItems` (type: `integer`):

Maximum total subdomain certificate records to return across the entire run.

## Actor input object example

```json
{
  "domains": [
    "apify.com"
  ],
  "resolveDns": true,
  "maxSubdomainsPerDomain": 25,
  "activeOnly": false,
  "excludeWildcards": true,
  "timeoutSec": 30,
  "maxConcurrency": 20,
  "maxItems": 100
}
```

# Actor output Schema

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

Structured JSON records produced by Certificate Transparency Logs Subdomain & SSL/TLS Asset Finder 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 = {};

// Run the Actor and wait for it to finish
const run = await client.actor("apex-b2b-data/ct-logs-subdomain-certificate-finder").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 = {}

# Run the Actor and wait for it to finish
run = client.actor("apex-b2b-data/ct-logs-subdomain-certificate-finder").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 '{}' |
apify call apex-b2b-data/ct-logs-subdomain-certificate-finder --silent --output-dataset

```

## MCP server setup

```json
{
    "mcpServers": {
        "apify": {
            "type": "http",
            "url": "https://mcp.apify.com/?tools=fetch-actor-details,apex-b2b-data/ct-logs-subdomain-certificate-finder"
        }
    }
}
```

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/bzQ5hbIUCsoSUe8Nk/builds/ubhSKKGQew9yOGuFQ/openapi.json