How to check when your domain and SSL certificate expire (and get warned in time)

Updated 2026-11-10 · Small business, landlords and freelancers · by CyberMax

Short answer

The domain's expiry date is in its registry record: look it up over RDAP (the successor to WHOIS), e.g. rdap.org/domain/example.com, and read the 'expiration' event. The certificate's end date is in the certificate the server presents: openssl s_client -connect example.com:443 -servername example.com | openssl x509 -noout -enddate. Then put both dates in a calendar or a monitor that re-reads them daily, because auto-renewal fails quietly.

Look up the registration expiry over RDAP.
Read the served certificate's notAfter date and check it covers the name.
Set alerts at 30, 7 and 1 day before.
Re-check daily: renewals can fail silently.

Copy-paste code

Read both dates from a terminal

# Domain registration expiry (RDAP, JSON)
curl -s https://rdap.org/domain/example.com | grep -o '"eventAction":"expiration","eventDate":"[^"]*'

# Certificate end date (the one the server presents)
echo | openssl s_client -connect example.com:443 -servername example.com 2>/dev/null \
  | openssl x509 -noout -enddate -ext subjectAltName

Good to know

Some country-code registries (for example .de) do not publish an expiry date over RDAP.

Let's Encrypt certificates last 90 days or less, so 'set a reminder once' does not work for them.

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Questions

Is WHOIS still used?

RDAP replaced WHOIS for generic TLDs; it returns structured JSON with the same dates.

Does a renewed certificate fix itself?

Only if the new certificate is installed: check the date the server presents, not just your CA account.

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