SSL certificates are a crucial part of securing online transactions and communications. Monitoring the validity of these certificates and error states is an important functionality provided by UptimeRobot. SSL certificate monitoring is available on our paid plans. If you're on a paid plan and enter a URL with HTTPS, these options are enabled by default when you create a monitor. On the Free plan, the Check SSL errors feature isn't available, so HTTPS monitors on Free are not checked for certificate issues. If you enter a URL with HTTP only, the SSL monitoring feature is disabled and cannot be enabled. By default, UptimeRobot combines SSL and domain monitoring in a single monitor, simplifying the process of ensuring both site security and availability.
Expiration Notifications:
UptimeRobot sends you notifications about the impending expiration of SSL certificates. This ensures that you can renew your SSL certificate in a timely manner to prevent any security lapses. The SSL expiration check is performed once every 24 hours. The reminder schedule is 30, 14, 7, and 0 days before expiration, but how early the first warning actually arrives depends on your certificate issuer. For most automatically renewed certificates (including Let's Encrypt and Cloudflare-issued certificates), the first warning arrives 14 days before expiry, not 30. Some issuers (such as cPanel-issued certificates) don't warn until 7 days out. You can edit or add your own custom reminder days by specifying any number of days that suits your needs.
SSL Error Detection:
In addition to monitoring certificate expiration, UptimeRobot also monitors for SSL errors on a website. An SSL error is an issue that arises when a browser isn't able to establish a secure connection with a website due to issues with the website’s SSL certificate. This could be because the certificate is expired, invalid, or improperly configured. When an SSL error is detected, the monitor switches to DOWN status and sends a notification. One common cause of SSL errors is incorrect URL formatting. SSL monitoring requires the URL to include https://. Without this prefix, UptimeRobot cannot check the SSL certificate, and monitoring will fail. Ensure that URLs are formatted correctly to avoid such errors.
To troubleshoot and fix SSL errors, you can refer to our blog post: SSL Certificate Errors
SSL Host-Mismatch:
Following a recent update, monitors with Check SSL errors enabled go DOWN with SSL Host-Mismatch when the website's certificate is issued for a different hostname than the one you monitor. Before this change, we didn't detect host mismatches, and the monitor stayed UP.
This applies to HTTP, Keyword, and API monitors with Check SSL errors enabled.
If your site works but the monitor is DOWN, the certificate doesn't cover the hostname in your monitor. Browsers show the same problem: "Your connection is not private".
To fix it, do any of these:
Fix the certificate so it covers the monitored hostname.
Monitor the hostname the certificate is valid for (for example, www.example.com).
Disable Check SSL errors if the mismatch is expected.
After the fix, the monitor goes back UP automatically on the next check.
With such preventive measures in place, you can ensure an uninterrupted, secure service for your users.