Which Certificate Transparency logs does ctlogs.dev monitor?

ctlogs.dev monitors 117.7 billion log entries and 28.5 billion certificates across the Google and Apple CT log lists: all 88 active logs, ingested continuously, and 111 archived and read-only logs. Coverage and freshness per log are published at https://ctlogs.dev/logs.

How fast is the ctlogs.dev API?

The ctlogs.dev API is fast: server-side domain lookup takes 25-30 ms and subdomains 45-50 ms on real queries (measured 2026-09-03). Requests go through Cloudflare, so end-to-end latency adds the network round trip.

How far back does the certificate history go?

The certificate history goes back to 2013. The index contains 6.5 billion distinct hostnames with first-seen and last-seen dates.

Can I list all subdomains of a domain?

Yes, you can list all subdomains. The /subdomains endpoint lists every hostname that ever appeared in a certificate under a domain, with certificate counts and first/last seen dates; the full list with paging is available through the API at GET /v1/hosts/{domain}.

Yes, the API is free. Anonymous use is free with fair rate limits and no key required; API keys raise the monthly quota. Full documentation is available at https://api.ctlogs.dev/ with machine-readable documentation at https://api.ctlogs.dev/llms.txt for AI agents.

Security, Privacy & Compliance

ctlogs.dev

Search billions of TLS certificates from all public Certificate Transparency logs by domain, wildcard, organization, serial number or SHA-256 fingerprint

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A free JSON API and web search engine indexing 28.5 billion TLS certificates from all public Certificate Transparency logs, searchable by domain, organization

Overview

A look at ctlogs.dev

ctlogs.dev continuously ingests every public Certificate Transparency log operated by Google, Cloudflare, DigiCert, Let's Encrypt, Sectigo and others into a single searchable index. The service indexes 28.5 billion certificates across 88 active logs and 111 archived logs, with 6.5 billion distinct hostnames and certificates dating back to 2013.

Users can search by domain (including wildcard searches for subdomains), organization name, certificate serial number, SHA-256 fingerprint, or public key. The web interface offers a subdomain finder showing every hostname ever certified under a domain, a BIMI brand logo browser for verified mark certificates, and a CAA record checker.

The API is free for anonymous use with fair rate limits and no key required. Signed-in users and API keys unlock higher quotas. All results come from public Certificate Transparency logs and are provided as received, with no guarantee of completeness or accuracy.

Feature notes

Search by domain, wildcard, organization, serial number, SHA-256 fingerprint and public key (SPKI)
Index of 28.5 billion certificates across 88 active and 111 archived CT logs
6.5 billion distinct hostnames with first-seen and last-seen dates, certificates back to 2013
Fast API: domain lookup 25-30 ms, subdomains 45-50 ms
Subdomain finder with certificate counts and first/last seen dates
BIMI brand logos from verified mark certificate logs
CAA record checker showing records as CAs see them and CAs that issued for a domain
Free JSON API with cursor pagination and anonymous use
Machine-readable documentation at llms.txt for AI agents
Continuous ingestion of all public CT logs with live coverage metrics

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ctlogs.dev at a glance

Community votes: 0
Followers: 0
HQ: France

ctlogs.dev metrics

Inspection sheet for ctlogs.dev: Ahrefs Domain Rating and Majestic link metrics, with the delta since the last inspection.
Metric	Value
Domain Rating	38 no change since last check
Trust Flow	18 no change since last check
Citation Flow	29 no change since last check
Referring domains	76 no change since last check
External backlinks	200 no change since last check

Domain Rating by Ahrefs inspected 6 Nov 2026, adjusted 6 Nov 2026. Primary topic: Regional/Europe (18). Majestic inspected 6 Nov 2026, adjusted 6 Nov 2026. Link data: Majestic. Trust Flow, Citation Flow and Topical Trust Flow are trademarks of Majestic-12 Ltd.

ctlogs.dev domain diagnostics

Run through the diagnostics

Public RDAP record, last read 6 Nov 2026, 16:50 UTC.
Domain age	6 months
Registered	27 Apr 2026
Expires	27 Apr 2027
Registrar	Porkbun LLC
DNSSEC	Not signed

Run the full check on ctlogs.dev

ctlogs.dev post-launch diagnostics

Measured after ctlogs.dev went live on Launching Pro on 6 November 2026.

Domain Rating (Ahrefs): 38; First measured 6 Nov 2026
Trust Flow (Majestic): 18; First measured 6 Nov 2026
Referring domains (Majestic): 76; First measured 6 Nov 2026

Day 0 since launch. Next receipt: day 30, 6 Dec 2026. The figures report a change; they do not say what caused it, and many things can. No figure here is a guess.

Biggest gains on Launching Pro

Launch tips, free to read

The playbook on Launching Pro lists what to prepare, what to post on launch day and where else to list your product.

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FAQ

Which Certificate Transparency logs does ctlogs.dev monitor?: ctlogs.dev monitors 117.7 billion log entries and 28.5 billion certificates across the Google and Apple CT log lists: all 88 active logs, ingested continuously, and 111 archived and read-only logs. Coverage and freshness per log are published at https://ctlogs.dev/logs.
How fast is the ctlogs.dev API?: The ctlogs.dev API is fast: server-side domain lookup takes 25-30 ms and subdomains 45-50 ms on real queries (measured 2026-09-03). Requests go through Cloudflare, so end-to-end latency adds the network round trip.
How far back does the certificate history go?: The certificate history goes back to 2013. The index contains 6.5 billion distinct hostnames with first-seen and last-seen dates.
Can I list all subdomains of a domain?: Yes, you can list all subdomains. The /subdomains endpoint lists every hostname that ever appeared in a certificate under a domain, with certificate counts and first/last seen dates; the full list with paging is available through the API at GET /v1/hosts/{domain}.
Is the API free?: Yes, the API is free. Anonymous use is free with fair rate limits and no key required; API keys raise the monthly quota. Full documentation is available at https://api.ctlogs.dev/ with machine-readable documentation at https://api.ctlogs.dev/llms.txt for AI agents.

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