Microproduct data guidebeginner

Certificate Transparency Search

Issued TLS certificates indexed from public CT logs for building domain certificate monitors and issuance alerts.

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At a glance

Difficulty
Beginner — comfortable for a first prototype
Size
Tiny · ≤0.05 GB
Formats
JSON
Access
API
API key
Not required
Provider
Sectigo crt.sh
Updates
Continuous
Data terms
Certificate Transparency log public data / crt.sh use

From source to product signal

Test a product idea in four steps

crt.sh queries public Certificate Transparency logs. Start with one registered domain and a JSON search. CT logs are the origin; crt.sh is the query surface. Logs can lag, expired certificates remain, and this is not a complete inventory of every private PKI.

1

Check the setup

  • Python 3.10 or newer
  • A notebook environment such as Jupyter or Google Colab
  • A domain you are authorized to inspect
2

Access the data

  1. 1.Open crt.sh and try one Identity search in the browser.
  2. 2.Request JSON for that domain with output=json.
  3. 3.Keep issuer name, common name, and not-after date.
Open official source
3

Run the Python example

Install the packages, then run the notebook cell.

python -m pip install pandas requests

import pandas as pd
import requests

response = requests.get(
    "https://crt.sh/",
    params={"q": "example.com", "output": "json"},
    timeout=60,
)
response.raise_for_status()
certificates = pd.DataFrame(response.json())
certificates["retrieved_at_utc"] = pd.Timestamp.now(tz="UTC")
print(certificates[["issuer_name", "common_name", "not_after"]].head())
4

Test a useful signal

List certificates for one domain

Test whether a CT search can power a bounded issuance monitor.

  1. 01Deduplicate certificate ids and keep issuer, common name, and expiry.
  2. 02Flag certificates whose not-after date is in the past.
  3. 03Explain that CT coverage depends on participating logs and is not a private-PKI inventory.

Dataset details

Sectigo crt.sh is a company source. Last verified 2026-08-18. Temporal coverage: certificates submitted to participating CT logs.

Theme

Technology & Cybersecurity

Domains

CybersecurityInternet Infrastructure

Data types

Event DataRegistry DataTabular

Tasks

Certificate MonitoringAlertingAsset Discovery

Geography

Global

Formats

JSON

Provider

Sectigo crt.sh

Data terms

Certificate Transparency log public data / crt.sh use