crt.guru is a SaaS platform focused on continuous TLS/SSL certificate monitoring. It performs external scans of user-defined endpoints — including HTTPS, LDAPS, SMTP STARTTLS, and IMAPS — from multiple geographic regions (Frankfurt, New York, Amsterdam, and others), without requiring any agents, server access, or code changes. Core capabilities include: - Certificate expiry monitoring with email alerts at 30, 14, 7, and 1 day before expiration - Vulnerability detection covering known issues such as Heartbleed, ROBOT, CCS Injection, and weak cipher suites - Multi-region scanning to detect discrepancies such as CDN edge nodes serving stale certificates - Certificate revocation monitoring (OCSP, CRL) - Certificate Transparency (CT) log monitoring to detect unauthorized certificate issuance for monitored domains - Compliance reporting in PDF format aligned with PCI DSS 4.0, NIST, and Mozilla guidelines - Scan history retention of up to 365 days depending on plan tier - Multi-channel alerting via email, Telegram, Discord, and Slack - REST API and webhook integrations The platform is structured around tiered subscription plans (Free, Starter, Pro, Business, Enterprise), with scan frequency ranging from daily on the free tier to every 30 minutes on the Enterprise tier. It targets a range of users from individual freelancers to security teams, MSPs, and agencies managing large certificate portfolios. The service was created by Pavel Buchnev and is positioned as an alternative to manual certificate management and point-in-time tools like SSL Labs, emphasizing continuous monitoring and audit-ready compliance documentation.