Overview
Free Certificate Transparency log search. Query SSL/TLS certificate issuance history for any domain. Returns issuer, validity dates, and serial numbers. No API key needed.
Notes: Add &output=json for JSON format. Free, rate limits apply for heavy scraping. Also supports identity matching and wildcard search.
TL;DR
What it does: crt.sh: Free Certificate Transparency log search.
Quick start: https://crt.sh/?q=example.com&output=json
No API key needed!
Try It Now
Call this URL to see what you get back:
https://crt.sh/?q=example.com&output=jsonFAQ
- Do I need an API key?
- No! This API is completely free to use with no authentication required.
- Is there a rate limit?
- Add &output=json for JSON format. Free, rate limits apply for heavy scraping. Also supports identity matching and wildcard search.
- Can I use this in a commercial project?
- Yes, these APIs are free for both personal and commercial use. Check the documentation for any specific restrictions.
- How do I get started?
- Copy the example URL above and paste it into your browser or code. The response is in JSON format which you can parse in any programming language.
Code Examples
JavaScript Example
fetch('https://crt.sh/?q=example.com&output=json')
.then(res => res.json())
.then(data => console.log(data))
.catch(err => console.error(err));Python Example
import requests
url = 'https://crt.sh/?q=example.com&output=json'
response = requests.get(url)
data = response.json()
print(data)API Details
- API URL
https://crt.sh/- Documentation
- https://crt.sh/
- Category
- Security
- Authentication
- Not Required
- Geographic Coverage
- global
What You Can Build
- Security audit tools
- Password strength checkers
- Certificate monitoring dashboards
- Security research projects