TLS Sentry
A free Python command-line tool that checks a website's HTTPS certificate and tells you exactly what's wrong with it — expired, untrusted, wrong hostname — instead of a generic connection error.
🔗 Visit TLS Sentry
Description
When a site's HTTPS certificate breaks, most tools just report "SSL handshake failed" and leave you to guess why. TLS Sentry answers that question directly: it connects twice, once checking everything properly and once without verification, and compares the two to pinpoint whether the problem is an expired certificate, a broken trust chain, or a hostname mismatch — then reports which one it is.
TLS Sentry is an open-source (MIT) Python CLI with zero runtime dependencies beyond the standard library, so it drops into any server or CI pipeline without a package install headache. It runs checks in parallel (8 jobs by default), outputs JSON for scripting, sends webhook notifications for alerting, and returns CI-friendly exit codes (0 clean, 1 findings, 2 usage error) so it slots straight into a cron job or pipeline gate. It's also importable as a Python library via a `check()` function for custom tooling. Scope is intentionally narrow: it checks only the leaf certificate, without OCSP/CRL revocation checking or IPv6 literal host:port support.
💬 Our review
The short version: TLS Sentry is a zero-dependency way to get a real diagnosis — not just a red X — when a certificate check fails, which is exactly what you want in a 3am cron alert.
Bigger monitoring platforms like UptimeRobot or Pingdom bundle certificate expiry checks alongside general uptime monitoring, but they're SaaS products with their own accounts and pricing tiers; TLS Sentry is a free, self-hosted CLI you drop into an existing cron job or CI pipeline with no dependencies to manage. It's the right pick if you already have monitoring infrastructure and just want sharper cert diagnostics without adding a new vendor. It's not a replacement for a full uptime/monitoring SaaS if you don't have one yet — and being a very new, small project, don't expect polish beyond what the README documents.
💰 Pricing
📊 Global score
🤖 AI-enriched data
Gratuit, licence MIT
Pros
Zéro dépendance, facile à déployer sur serveurs nus ou conteneurs
Diagnostic détaillé plutôt qu'une simple erreur de connexion générique
Vérification parallèle et alertes webhook pour usage cron/CI
Cons
Vérifie uniquement le certificat feuille, pas la chaîne intermédiaire
Pas de vérification de révocation OCSP ou CRL
Projet très récent, faible adoption pour l'instant