Certimon watches certificate expiry for free. When you need more than the expiry date, this is the trade.
Verified 19 Aug 2026
Certimon is a good, honest tool, and it is free — unlimited domains, no per-domain charge, no card. It checks each hostname hourly from outside, warns on a 30, 14, 7, and 1-day ladder to Telegram, Teams, PagerDuty, or a webhook, and flags a hostname mismatch or a self-signed certificate. Its makers are upfront that it does one thing: Certimon only does SSL expiry monitoring. If expiry is all you need, free is hard to argue with.
CertPost is a paid tool, so the fair question is what the money buys. It reads the whole certificate from a real handshake, not only the expiry date: the full chain including intermediates — an expired intermediate breaks the site while the leaf date still looks fine — plus hostname and SAN, and any unexpected change to the certificate, on any TLS port with the mail and admin ports included. Around the certificate it also watches domain-registration expiry, which is a separate clock from the certificate, Certificate Transparency issuance alerts, and DNS drift.
The trade is breadth rather than price. Certimon covers expiry, and covers it well. CertPost is one tool for the certificate, its chain, the domain, DNS, and the non-web ports, at three free then a flat $29/month. If expiry alerts are the whole job, Certimon does them. If a chain break, a swapped certificate, a lapsed domain, or a mail-port certificate is also yours to catch, a tool that watches all of it is less to stitch together.
Running both:
1. Keep Certimon for free expiry alerts if you like it.
2. Add CertPost for the chain, the mail and admin ports, the domain registration, and Certificate Transparency around the same certificates.
3. Send both to the same channel so an expiry warning and a chain break land in one place.
Import your domain list in 2 minutes — 3 certificates free, no card.
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