Expired certificate (Firefox)
SEC_ERROR_EXPIRED_CERTIFICATEFirefox's way of saying the certificate is past its expiry date or the system clock is wrong.
What it means
SEC_ERROR_EXPIRED_CERTIFICATE is Firefox's equivalent of Chrome's date error. The certificate's validity window has ended relative to the current time, so Firefox blocks the connection. As with the Chrome version, this is either a certificate that genuinely lapsed or a device whose clock is set wrong enough to make a valid certificate look expired.
When it happens
It happens when a certificate expired and wasn't renewed, or when automated renewal failed without anyone noticing. If the site works in other browsers or on other machines, suspect the local clock: a wrong date, time, or time zone, often after a battery or OS reset.
How to fix it
- Check the certificate's expiry date. If it's in the past, renew or reissue it and install the new certificate.
- If renewal is automated, find out why it didn't run and fix the underlying job or hook.
- If only one machine is affected, correct its date and time and turn on automatic time sync.
- Reload the web server after installing the new certificate so it stops serving the expired one.
Check this site’s certificate
Paste the domain and Sitewell shows the certificate’s expiry, the hostnames it covers, the chain, and the issuer — enough to pin down what triggered this error. Free, no signup.
Related errors
NET::ERR_CERT_DATE_INVALIDThe certificate's validity dates don't line up with the current time, usually because it expired or the device clock is wrong.
SSL_ERROR_BAD_CERT_DOMAINFirefox's name-mismatch error: the certificate doesn't cover the hostname you're visiting.
ERR_CERT_REVOKEDThe certificate authority pulled this certificate back before its expiry date, so the browser refuses to trust it.