# Subdomain Finder — Certificate Transparency (crt.sh) (`bgfc97/crtsh-subdomain-finder`) Actor

Discover subdomains of any domain from public Certificate Transparency logs (crt.sh). Attack-surface mapping and recon with first/last-seen dates. No key, no proxy.

- **URL**: https://apify.com/bgfc97/crtsh-subdomain-finder.md
- **Developed by:** [Bruno](https://apify.com/bgfc97) (community)
- **Categories:** Developer tools, SEO tools, Business
- **Stats:** 1 total users, 0 monthly users, 100.0% runs succeeded, 0 bookmarks
- **User rating**: No ratings yet

## Pricing

from $20.00 / 1,000 domain scanneds

This Actor is paid per event and usage. You are charged both the fixed price for specific events and for Apify platform usage.

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

## What's an Apify Actor?

Actors are web data automations that power AI and operations. They run on the Apify platform to scrape websites, process data, connect APIs, and automate workflows.
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.

- **AI agents and MCP clients** — the [Apify MCP server](https://docs.apify.com/integrations/mcp.md) at `https://mcp.apify.com` (remote, streamable HTTP, OAuth on first use).
- **Agentic workflows and local Actor development** — [Agent Skills](https://apify.com/.well-known/agent-skills/index.json) with the [Apify CLI](https://docs.apify.com/cli/docs.md): `npm install -g apify-cli`, then `apify login`.
- **JavaScript/TypeScript projects** — the official [JS/TS client](https://docs.apify.com/api/client/js/docs.md): `npm install apify-client`.
- **Python projects** — the official [Python client](https://docs.apify.com/api/client/python/docs.md): `pip install apify-client`.
- **Any other language** — 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 — Certificate Transparency (crt.sh)

Enumerate **subdomains** of any domain using public **Certificate Transparency** logs via [crt.sh](https://crt.sh). Every TLS certificate ever issued is logged publicly — this actor mines those logs to reveal a domain's subdomains. No key, no proxy, no brute force.

### Input

```json
{ "domains": ["github.com", "tesla.com"], "includeExpired": true }
```

### Output (one row per unique subdomain)

```json
{ "domain": "github.com", "subdomain": "api.github.com", "first_seen": "2021-03-01T00:00:00", "last_seen": "2025-06-10T23:59:59" }
```

### Use cases

- Attack-surface mapping / external recon (pentest, bug bounty)
- Asset & shadow-IT discovery for security teams
- Monitoring new subdomains of your brand or competitors

### Notes

- Data source: Certificate Transparency logs aggregated by crt.sh.
- crt.sh can be busy; requests are retried automatically.
- Billed per **domain scanned** (not per subdomain), so cost is predictable regardless of how many subdomains a domain has.

# Actor input Schema

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

Root domains to enumerate subdomains for. Example: example.com, github.com, tesla.com.

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

If ON, also includes subdomains from expired certificates (more complete history). If OFF, only currently valid certs.

## Actor input object example

```json
{
  "domains": [
    "github.com"
  ],
  "includeExpired": true
}
```

# 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": [
        "github.com"
    ]
};

// Run the Actor and wait for it to finish
const run = await client.actor("bgfc97/crtsh-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": ["github.com"] }

# Run the Actor and wait for it to finish
run = client.actor("bgfc97/crtsh-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": [
    "github.com"
  ]
}' |
apify call bgfc97/crtsh-subdomain-finder --silent --output-dataset

```

## MCP server setup

```json
{
    "mcpServers": {
        "apify": {
            "command": "npx",
            "args": [
                "mcp-remote",
                "https://mcp.apify.com/?tools=bgfc97/crtsh-subdomain-finder",
                "--header",
                "Authorization: Bearer <YOUR_API_TOKEN>"
            ]
        }
    }
}

```

## OpenAPI specification

Download the OpenAPI definition: https://api.apify.com/v2/actors/zhdlgeGNsXAu0sIuw/builds/aTpgnHtOOhALroKmB/openapi.json