crt.sh Has a Free API — Find Every SSL Certificate for Any Domain (With Python)

Crt.sh can search Certificate Transparency logs crt.sh queries public Certificate Transparency records for issued certificates.

Crt.sh API Provides a JSON API response, using a query with output=json returns JSON-formatted certificate records.

Crt.sh No API key is required to use crt.sh crt.sh allows free searches without authentication or API keys.

Python script can extract subdomains from API results, script parses name_value fields from JSON and collects unique subdomain names.

Monitor_new_certs function Scripts can filter certificates issued within a recent time window, function parses not_before timestamps and compares them against a cutoff datetime.