ctlogs.dev

ctlogs.dev is a free Certificate Transparency search engine and JSON API. It continuously ingests every public CT log on the Google and Apple log lists — including the sharded and static (tiled) logs — and indexes billions of TLS certificates into one searchable database.

You can look up certificates by hostname or wildcard (*.example.com), by the organization named in the certificate, by serial number or SHA-256 fingerprint, and by public key (SPKI hash) to find all certificates sharing one key. Each certificate page shows the full record — subject, issuer, validity, SANs, the CT logs it appeared in with their SCT timestamps — and lets you download the PEM/DER body when it is archived.

A built-in subdomain finder lists every hostname ever certified under a domain, with certificate counts, first/last seen dates, which makes it a practical tool for attack-surface mapping, asset inventory and phishing-domain hunting.

Everything is available programmatically at api.ctlogs.dev: plain JSON over HTTPS, cursor pagination, no registration needed for anonymous use, API keys for higher quotas. Typical server-side latency for domain and subdomain queries is in the tens of milliseconds. A public status page shows every monitored log with coverage and freshness, so you can see exactly which data the index is built from.

The service is operated by an independent developer in France, runs on EU infrastructure and does not require an account to use.