# 🔍 Subdomain Finder (`taroyamada/subdomain-finder`) Actor

Discover subdomains for any domain using Certificate Transparency logs (crt.sh). Find hidden subdomains for security audits, penetration testing, asset inventory. No API key needed.

- **URL**: https://apify.com/taroyamada/subdomain-finder.md
- **Developed by:** [太郎 山田](https://apify.com/taroyamada) (community)
- **Categories:** Developer tools, Automation
- **Stats:** 2 total users, 1 monthly users, 100.0% runs succeeded, NaN bookmarks
- **User rating**: No ratings yet

## Pricing

Pay per event

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/platform/actors/running/actors-in-store#pay-per-event

## What's an Apify Actor?

Actors are a software tools running on the Apify platform, for all kinds of web data extraction and automation use cases.
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.
Actors are written with capital "A".

## 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.
The best way to integrate Actors is as follows.

In JavaScript/TypeScript projects, use official [JavaScript/TypeScript client](https://docs.apify.com/api/client/js.md):

```bash
npm install apify-client
```

In Python projects, use official [Python client library](https://docs.apify.com/api/client/python.md):

```bash
pip install apify-client
```

In shell scripts, use [Apify CLI](https://docs.apify.com/cli/docs.md):

````bash
# MacOS / Linux
curl -fsSL https://apify.com/install-cli.sh | bash
# Windows
irm https://apify.com/install-cli.ps1 | iex
```bash

In AI frameworks, you might use the [Apify MCP server](https://docs.apify.com/platform/integrations/mcp.md).

If your project is in a different language, use the [REST API](https://docs.apify.com/api/v2.md).

For usage examples, see the [API](#api) section below.

For more details, see Apify documentation as [Markdown index](https://docs.apify.com/llms.txt) and [Markdown full-text](https://docs.apify.com/llms-full.txt).


# README

## 🔍 Subdomain Finder

Discover subdomains for any domain using Certificate Transparency logs (crt.sh). Essential for security audits, penetration testing, asset inventory.

### Store Quickstart

Start with the **Quickstart** template (single domain). For large asset inventories, use **Enterprise Audit** with up to 50 domains.

### Key Features

- 🔍 **Certificate Transparency logs** — Uses crt.sh — the authoritative CT log database
- 📊 **Full subdomain history** — Active AND expired certificates both discoverable
- 🏷️ **Issuer tracking** — See which CA issued each certificate
- 📅 **Validity dates** — validFrom / validTo per certificate
- 🎯 **Deduplication** — Unique subdomains only, no duplicates
- 🔑 **No API key needed** — Free public CT log database

### Use Cases

| Who | Why |
|-----|-----|
| **Penetration testers** | Discover forgotten subdomains as attack surface |
| **Asset inventory teams** | Full catalog of company-wide subdomains |
| **Bug bounty hunters** | Find in-scope targets via CT logs |
| **M&A due diligence** | Audit acquired company's public infrastructure |
| **DNS auditors** | Cross-reference CT logs with DNS records to find orphaned subdomains |

### Input

| Field | Type | Default | Description |
|-------|------|---------|-------------|
| domains | string[] | (required) | Domains to scan (max 50) |
| includeExpired | boolean | false | Include expired certificates |
| dedup | boolean | true | Deduplicate subdomain names |

### Input Example

```json
{
  "domains": ["example.com", "target.org"],
  "includeExpired": false,
  "dedup": true
}
````

### Output Example

```json
{
  "domain": "example.com",
  "subdomains": [
    {"name": "api.example.com", "issuer": "Let's Encrypt", "validFrom": "2026-01-01", "validTo": "2026-04-01"},
    {"name": "mail.example.com", "issuer": "DigiCert", "validFrom": "2025-06-01", "validTo": "2026-06-01"}
  ],
  "totalFound": 42
}
```

### FAQ

**Will I find ALL subdomains?**

Only those with valid HTTPS certificates. HTTP-only subdomains and those using wildcard certs are missed.

**What about wildcard certificates?**

Wildcard certs (\*.example.com) appear as a single entry. Individual subdomains under them may not be listed.

**Is crt.sh reliable?**

Yes — it aggregates all public CT logs required by browser vendors. Very comprehensive.

**Can I scan a competitor's domain?**

Publicly — yes, CT logs are public by design. Always comply with your jurisdiction's laws.

### Related Actors

DevOps & Tech Intel cluster — explore related Apify tools:

- [🌐 DNS Propagation Checker](https://apify.com/taroyamada/dns-propagation-checker) — Check DNS propagation across 8 global resolvers (Google, Cloudflare, Quad9, OpenDNS).
- [🧹 CSV Data Cleaner](https://apify.com/taroyamada/csv-data-cleaner) — Clean CSV data: trim whitespace, remove empty rows, deduplicate by columns, sort.
- [📦 NPM Package Analyzer](https://apify.com/taroyamada/npm-package-intelligence) — Analyze npm packages: download stats, dependencies, licenses, deprecation status.
- [📊 SEC EDGAR Monitor](https://apify.com/taroyamada/sec-edgar-filings-monitor) — Monitor SEC EDGAR filings for US public companies by ticker or CIK.

### Cost

**Pay Per Event**:

- `actor-start`: $0.01 (flat fee per run)
- `dataset-item`: $0.003 per output item

**Example**: 1,000 items = $0.01 + (1,000 × $0.003) = **$3.01**

No subscription required — you only pay for what you use.

# Actor input Schema

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

Root domains to find subdomains for (max 50).

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

Include expired entries

## `delivery` (type: `string`):

Where to send results: dataset or webhook

## `webhookUrl` (type: `string`):

Webhook URL to POST results to (if delivery=webhook)

## `dryRun` (type: `boolean`):

Run without saving results (for testing)

## Actor input object example

```json
{
  "domains": [
    "example.com"
  ],
  "includeExpired": false,
  "delivery": "dataset",
  "dryRun": false
}
```

# 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 = {
    "domains": [
        "example.com"
    ]
};

// Run the Actor and wait for it to finish
const run = await client.actor("taroyamada/subdomain-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 = { "domains": ["example.com"] }

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

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

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

```

## CLI example

```bash
echo '{
  "domains": [
    "example.com"
  ]
}' |
apify call taroyamada/subdomain-finder --silent --output-dataset

```

## MCP server setup

```json
{
    "mcpServers": {
        "apify": {
            "command": "npx",
            "args": [
                "mcp-remote",
                "https://mcp.apify.com/?tools=taroyamada/subdomain-finder",
                "--header",
                "Authorization: Bearer <YOUR_API_TOKEN>"
            ]
        }
    }
}

```

## OpenAPI specification

```json
{
    "openapi": "3.0.1",
    "info": {
        "title": "🔍 Subdomain Finder",
        "description": "Discover subdomains for any domain using Certificate Transparency logs (crt.sh). Find hidden subdomains for security audits, penetration testing, asset inventory. No API key needed.",
        "version": "0.1",
        "x-build-id": "XEHsY17a3wJIRQqig"
    },
    "servers": [
        {
            "url": "https://api.apify.com/v2"
        }
    ],
    "paths": {
        "/acts/taroyamada~subdomain-finder/run-sync-get-dataset-items": {
            "post": {
                "operationId": "run-sync-get-dataset-items-taroyamada-subdomain-finder",
                "x-openai-isConsequential": false,
                "summary": "Executes an Actor, waits for its completion, and returns Actor's dataset items in response.",
                "tags": [
                    "Run Actor"
                ],
                "requestBody": {
                    "required": true,
                    "content": {
                        "application/json": {
                            "schema": {
                                "$ref": "#/components/schemas/inputSchema"
                            }
                        }
                    }
                },
                "parameters": [
                    {
                        "name": "token",
                        "in": "query",
                        "required": true,
                        "schema": {
                            "type": "string"
                        },
                        "description": "Enter your Apify token here"
                    }
                ],
                "responses": {
                    "200": {
                        "description": "OK"
                    }
                }
            }
        },
        "/acts/taroyamada~subdomain-finder/runs": {
            "post": {
                "operationId": "runs-sync-taroyamada-subdomain-finder",
                "x-openai-isConsequential": false,
                "summary": "Executes an Actor and returns information about the initiated run in response.",
                "tags": [
                    "Run Actor"
                ],
                "requestBody": {
                    "required": true,
                    "content": {
                        "application/json": {
                            "schema": {
                                "$ref": "#/components/schemas/inputSchema"
                            }
                        }
                    }
                },
                "parameters": [
                    {
                        "name": "token",
                        "in": "query",
                        "required": true,
                        "schema": {
                            "type": "string"
                        },
                        "description": "Enter your Apify token here"
                    }
                ],
                "responses": {
                    "200": {
                        "description": "OK",
                        "content": {
                            "application/json": {
                                "schema": {
                                    "$ref": "#/components/schemas/runsResponseSchema"
                                }
                            }
                        }
                    }
                }
            }
        },
        "/acts/taroyamada~subdomain-finder/run-sync": {
            "post": {
                "operationId": "run-sync-taroyamada-subdomain-finder",
                "x-openai-isConsequential": false,
                "summary": "Executes an Actor, waits for completion, and returns the OUTPUT from Key-value store in response.",
                "tags": [
                    "Run Actor"
                ],
                "requestBody": {
                    "required": true,
                    "content": {
                        "application/json": {
                            "schema": {
                                "$ref": "#/components/schemas/inputSchema"
                            }
                        }
                    }
                },
                "parameters": [
                    {
                        "name": "token",
                        "in": "query",
                        "required": true,
                        "schema": {
                            "type": "string"
                        },
                        "description": "Enter your Apify token here"
                    }
                ],
                "responses": {
                    "200": {
                        "description": "OK"
                    }
                }
            }
        }
    },
    "components": {
        "schemas": {
            "inputSchema": {
                "type": "object",
                "required": [
                    "domains"
                ],
                "properties": {
                    "domains": {
                        "title": "Domains",
                        "type": "array",
                        "description": "Root domains to find subdomains for (max 50).",
                        "items": {
                            "type": "string"
                        }
                    },
                    "includeExpired": {
                        "title": "Include Expired Certificates",
                        "type": "boolean",
                        "description": "Include expired entries",
                        "default": false
                    },
                    "delivery": {
                        "title": "Delivery Mode",
                        "enum": [
                            "dataset",
                            "webhook"
                        ],
                        "type": "string",
                        "description": "Where to send results: dataset or webhook",
                        "default": "dataset"
                    },
                    "webhookUrl": {
                        "title": "Webhook URL",
                        "type": "string",
                        "description": "Webhook URL to POST results to (if delivery=webhook)"
                    },
                    "dryRun": {
                        "title": "Dry Run",
                        "type": "boolean",
                        "description": "Run without saving results (for testing)",
                        "default": false
                    }
                }
            },
            "runsResponseSchema": {
                "type": "object",
                "properties": {
                    "data": {
                        "type": "object",
                        "properties": {
                            "id": {
                                "type": "string"
                            },
                            "actId": {
                                "type": "string"
                            },
                            "userId": {
                                "type": "string"
                            },
                            "startedAt": {
                                "type": "string",
                                "format": "date-time",
                                "example": "2025-01-08T00:00:00.000Z"
                            },
                            "finishedAt": {
                                "type": "string",
                                "format": "date-time",
                                "example": "2025-01-08T00:00:00.000Z"
                            },
                            "status": {
                                "type": "string",
                                "example": "READY"
                            },
                            "meta": {
                                "type": "object",
                                "properties": {
                                    "origin": {
                                        "type": "string",
                                        "example": "API"
                                    },
                                    "userAgent": {
                                        "type": "string"
                                    }
                                }
                            },
                            "stats": {
                                "type": "object",
                                "properties": {
                                    "inputBodyLen": {
                                        "type": "integer",
                                        "example": 2000
                                    },
                                    "rebootCount": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "restartCount": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "resurrectCount": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "computeUnits": {
                                        "type": "integer",
                                        "example": 0
                                    }
                                }
                            },
                            "options": {
                                "type": "object",
                                "properties": {
                                    "build": {
                                        "type": "string",
                                        "example": "latest"
                                    },
                                    "timeoutSecs": {
                                        "type": "integer",
                                        "example": 300
                                    },
                                    "memoryMbytes": {
                                        "type": "integer",
                                        "example": 1024
                                    },
                                    "diskMbytes": {
                                        "type": "integer",
                                        "example": 2048
                                    }
                                }
                            },
                            "buildId": {
                                "type": "string"
                            },
                            "defaultKeyValueStoreId": {
                                "type": "string"
                            },
                            "defaultDatasetId": {
                                "type": "string"
                            },
                            "defaultRequestQueueId": {
                                "type": "string"
                            },
                            "buildNumber": {
                                "type": "string",
                                "example": "1.0.0"
                            },
                            "containerUrl": {
                                "type": "string"
                            },
                            "usage": {
                                "type": "object",
                                "properties": {
                                    "ACTOR_COMPUTE_UNITS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATASET_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATASET_WRITES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "KEY_VALUE_STORE_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "KEY_VALUE_STORE_WRITES": {
                                        "type": "integer",
                                        "example": 1
                                    },
                                    "KEY_VALUE_STORE_LISTS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "REQUEST_QUEUE_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "REQUEST_QUEUE_WRITES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATA_TRANSFER_INTERNAL_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATA_TRANSFER_EXTERNAL_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "PROXY_RESIDENTIAL_TRANSFER_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "PROXY_SERPS": {
                                        "type": "integer",
                                        "example": 0
                                    }
                                }
                            },
                            "usageTotalUsd": {
                                "type": "number",
                                "example": 0.00005
                            },
                            "usageUsd": {
                                "type": "object",
                                "properties": {
                                    "ACTOR_COMPUTE_UNITS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATASET_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATASET_WRITES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "KEY_VALUE_STORE_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "KEY_VALUE_STORE_WRITES": {
                                        "type": "number",
                                        "example": 0.00005
                                    },
                                    "KEY_VALUE_STORE_LISTS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "REQUEST_QUEUE_READS": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "REQUEST_QUEUE_WRITES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATA_TRANSFER_INTERNAL_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "DATA_TRANSFER_EXTERNAL_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "PROXY_RESIDENTIAL_TRANSFER_GBYTES": {
                                        "type": "integer",
                                        "example": 0
                                    },
                                    "PROXY_SERPS": {
                                        "type": "integer",
                                        "example": 0
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}
```