On older devices, you may start to receive errors in your browser such as “Your connection is not private” or ERR_CERT_DATE_INVALID when viewing a website secured with a Let’s Encrypt SSL certificate. This can still occur, even when the certificate itself is valid and the date on the device is correct.

This may look like:

let's encrypt certificate secured website displaying err_cert_date_invalid

As of 30 September 2021, the original root certificate for Let’s Encrypt is no longer valid. All devices which are up-to-date won’t have any issues whatsoever.


The only workaround is to update your device (eg via windows updates or macOS updates) to the latest version.

Unfortunately, if your device cannot be updated (for example, it’s too old) then there’s no safe workaround. Devices and systems known to have issues (but not limited to) are:

  • Windows XP
  • Apple macOS 10.12 or lower
  • iPhone / iPad iOS versions 9 or lower
  • Android 7.1.1 and lower
  • Mozilla Firefox versions below 50
  • Windows Live Mail
  • Old Java software

We highly recommend replacing the device so that it can continue to receive security updates.


Accepting invalid certificates can present as a security risk, as there’s no way to verify them. Conetix does not recommend you do this.

Further Reading

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