# crt.sh Cert Monitor — Subdomain & SSL Cert Discovery (`vhsgreed/crtsh-cert-monitor`) Actor

Monitor certificate-transparency logs via crt.sh (keyless, no API key) for any domain: newly issued subdomains, certificate issuers, first/last-seen dates and cert IDs. Flat one-record-per-cert output for CSV/Excel/JSON export. Ideal for attack-surface discovery and brand monitoring.

- **URL**: https://apify.com/vhsgreed/crtsh-cert-monitor.md
- **Developed by:** [Karl Sundström](https://apify.com/vhsgreed) (community)
- **Categories:**
- **Stats:** 1 total users, 0 monthly users, 0.0% runs succeeded, 0 bookmarks
- **User rating**: No ratings yet

## Pricing

from $0.15 / 1,000 certificate records

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?

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

## crt.sh Certificate Transparency Monitor — New Subdomain & SSL Cert Discovery

> Independent tool, not affiliated with crt.sh or Sectigo.

Monitor **certificate-transparency logs for any domain via crt.sh** — keyless, no API key, no login. Extract newly issued subdomains, certificate issuers, validity windows and cert IDs, and get a flat one-record-per-certificate output ready for CSV/Excel/JSON export. New CT-log entries are warm signals: every fresh certificate reveals a hostname that just went live.

### Why crt.sh Certificate Transparency Monitor?

- 🕵️ **Attack-surface discovery** — catch subdomains the moment certificates appear in public CT logs.
- 🔔 **Change monitoring** — run it on a schedule with `hoursBack` to get only certificates issued since your last check.
- 🏢 **Brand & phishing tracking** — watch lookalike domains' certificate activity for security and brand teams.
- 📋 **Flat output** — one row per certificate (`domain`, `subdomain`, `issuer`, `crtId`) built for CRM, sheets and SIEM import.
- ⚡ **No setup** — queries crt.sh's open JSON endpoint directly; just enter a domain and run.

### Use cases

Attack-surface management · subdomain enumeration · brand/typosquat monitoring · security compliance audits · OSINT research · expired-cert alerting

### What data you get

| 🏷️ Field | Description |
| --- | --- |
| 🌐 domain | Domain you asked to monitor |
| 🔎 subdomain | Host names covered by the certificate (SAN list) |
| 🏛️ issuer | Certificate-issuing CA (e.g. Let's Encrypt, DigiCert) |
| 📅 notBefore | Certificate validity start |
| 📅 notAfter | Certificate expiry |
| 🕐 entryTimestamp | When the log entry landed in CT logs (if present) |
| 🆔 crtId | crt.sh certificate ID — open `https://crt.sh/?id=<crtId>` for the full cert |

### How to use

1. Add the actor to your Apify account and click **Run**.
2. Enter one or more `domainList` entries (e.g. `wikipedia.org`).
3. Set `hoursBack` to filter recent certificates (default 720 h = 30 days; `0` = full history).
4. Set `maxResults` to cap the bill (default 100).
5. Export results as JSON, CSV or Excel, or schedule runs for continuous monitoring.

### Input

```json
{
  "domainList": ["wikipedia.org"],
  "hoursBack": 720,
  "maxResults": 100
}
```

| Field | Type | Description | Default |
| --- | --- | --- | --- |
| `domainList` | array | Domains to monitor (all subdomains included via `%25.<domain>` CT search) | required |
| `hoursBack` | integer | Only certificates issued within the last N hours; `0` returns full history | 720 |
| `maxResults` | integer | Cap on records per run | 100 |

### Output

```json
{
  "domain": "wikipedia.org",
  "subdomain": "*.m.wikipedia.org *.wikipedia.org wikipedia.org",
  "issuer": "C=US, O=Let's Encrypt, CN=YE2",
  "notBefore": "2026-08-05T19:15:41",
  "notAfter": "2026-11-03T19:15:40",
  "entryTimestamp": null,
  "crtId": "28567885787"
}
```

| | Typical subdomain scrapers | This actor |
| --- | --- | --- |
| Source | DNS brute-force wordlists | Official certificate-transparency logs |
| Coverage | Only guessable names | Every hostname that ever got a TLS certificate |
| API key | Varies | None |
| Output | Mixed formats | Flat one-row-per-cert, export-ready |

### Support

Issues and feature requests via the Apify actor page.

# Actor input Schema

## `domainList` (type: `array`):

Domains to monitor, e.g. wikipedia.org — each is queried for all its subdomains via certificate-transparency logs

## `hoursBack` (type: `integer`):

Only return certificates issued within the last N hours (default 720 = 30 days; 0 returns the full CT history)

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

Cap on certificate records returned per run (default 100)

## Actor input object example

```json
{
  "hoursBack": 720,
  "maxResults": 100
}
```

# Actor output Schema

## `records` (type: `string`):

Dataset of certificate-transparency records (one per certificate).

## `recordsJson` (type: `string`):

Full dataset items as raw JSON.

## `runView` (type: `string`):

Inspect this run, its logs and storages in Apify Console.

# 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("vhsgreed/crtsh-cert-monitor").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("vhsgreed/crtsh-cert-monitor").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 vhsgreed/crtsh-cert-monitor --silent --output-dataset

```

## MCP server setup

```json
{
    "mcpServers": {
        "apify": {
            "type": "http",
            "url": "https://mcp.apify.com/?tools=fetch-actor-details,vhsgreed/crtsh-cert-monitor"
        }
    }
}

```

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/0OFVhlrwrjgd8qJRs/builds/h9Z6HvBl75bvtGL62/openapi.json