Short answer. A good SSL certificate monitoring service warns you ahead of expiry and chain problems, so your site never goes down because of a lapsed certificate. Strong options include enterno.io (free tier of 10 monitors, alerts via Telegram/Slack/email/webhook), UptimeRobot (a generous free plan), and Ping and Datadog (enterprise paid platforms). Your choice depends on how many domains you have, which alert channels you need, and your budget.
Monitoring vs a one-off check
A one-off SSL check shows the certificate's state at a single moment. But Let's Encrypt certificates last only 90 days and auto-renewal sometimes breaks — cron fails, the web-server config changes, a token expires. SSL certificate monitoring continuously tracks expiry, the chain of trust and SSL/TLS проверку availability, then alerts you 7–30 days before expiry. That turns a potential outage into a routine task. Read more in our article on SSL certificate monitoring.
The main cause of sudden SSL outages isn't the certificate itself — it's broken auto-renewal: the certbot cron job fails silently, and you only learn about it once the site is already down. Monitoring catches this in advance.
You can quickly read the expiry date of a locally installed certificate with a single command:
openssl x509 -enddate -noout -in cert.pemIt prints a line like notAfter=... — handy for a manual check on the server, but continuous monitoring is what removes the need to remember it at all.
What matters when choosing
- Alert lead time — how many days before expiry you're warned (ideally a configurable threshold).
- Alert channels — email, Telegram, Slack, webhook, PagerDuty, Jira.
- Check frequency — from every minute to once a day.
- Depth — expiry only, or also the chain, protocols and weak ciphers.
- Price and limits — how many domains the free tier covers.
- Payment methods — critical for Russian teams whose foreign cards no longer work.
SSL monitoring comparison
| Service | Free tier | Alert channels | Check frequency | Type |
|---|---|---|---|---|
| enterno.io | 10 monitors | Telegram, Slack, email, webhook, PagerDuty, Jira | Frequent | Monitoring + 48 tools |
| UptimeRobot | Up to 50 monitors | Email, integrations | 5-minute | Uptime + SSL |
| Pingdom | Trial only | Email, SMS, integrations | Configurable | Enterprise paid |
| Datadog | Trial | Many integrations | Configurable | Enterprise paid |
| StatusCake | Limited | Email, integrations | Configurable | Uptime + SSL |
Service overview
- enterno.io — a free tier of 10 monitors with alerts via Telegram, Slack, email, webhook, PagerDuty and Jira. Beyond SSL it also tracks uptime, DNS and ping, so it covers monitoring as a whole rather than certificates alone, and it ships a public REST API документацию plus an MCP server for Claude/Cursor. Paid plans: Pioneer 299₽, Starter 490₽, Pro 1490₽, Business 3990₽/mo.
- UptimeRobot — well known for its generous free plan (up to 50 monitors, 5-minute interval). SSL monitoring is included; the trade-off is no local-card payment for RU teams.
- Pingdom — a mature enterprise solution from SolarWinds with detailed analytics and history. Paid only after a trial, aimed at large teams.
- Datadog — an enterprise observability platform; SSL checks are part of its synthetic monitoring. A fit for teams that want metrics, logs and traces in one system.
- StatusCake — combines uptime and SSL expiry checks, with a limited free plan for smaller projects.
Which to choose
For frequent checks across multiple alert channels including Telegram, choose enterno.io. For the most free uptime monitors, UptimeRobot. For a large team with budget and a need for deep analytics, Pingdom or Datadog. Before setting up monitoring it helps to review the SSL/TLS basics once, and if you use free certificates, read about setting up Let's Encrypt — the auto-renewal of free certificates is the most common source of incidents.
Tip: configure two alert thresholds — 30 days (time to reissue calmly) and 7 days (a critical signal that auto-renewal has failed).
FAQ
How many days before expiry does the alert arrive?
Most services make the threshold configurable. A common practice is two notifications: at 30 days and at 7 days. enterno.io lets you set your own warning and critical thresholds.
Can I monitor SSL for free?
Yes. The free tiers of enterno.io (10 monitors) and UptimeRobot (up to 50) cover the needs of a small to mid-sized site at no cost.
Does monitoring only check expiry?
Good services also check the chain of trust, HTTPS availability and sometimes protocol versions. If a certificate has already expired, see our fix guide.
What if Let's Encrypt auto-renewal breaks?
Monitoring exists precisely to catch that failure early. On the alert, reissue the certificate manually and check the certbot cron job. Core terms are in the SSL glossary.