SSL Certificate Checker
Check a domain's SSL/TLS certificate - issuer, validity dates, and how many days until it expires.
Why check your SSL certificate?
An expired or misconfigured TLS certificate breaks HTTPS on your domain, and in email that shows up in the worst place: your tracking links and landing pages. A recipient who clicks a link and hits a browser security warning almost never continues, and the click looks like a failure in your reporting.
This tool connects to your domain over TLS and reports the certificate's issuer, subject, validity window, and how many days remain until it expires - so you can catch a problem before your prospects do.
What the checker reports
The issuer is the certificate authority that signed the certificate (Let's Encrypt, DigiCert, Google Trust Services, and so on). The subject is the domain the certificate is valid for - watch for a mismatch, where the certificate covers www but not the apex, or a different domain entirely.
The validity window is the not-before and not-after dates, and the days remaining is the number that matters day to day. Anything under about 14 days is worth acting on, because a renewal that hasn't happened yet is a renewal that might silently fail.
Why certificates expire unexpectedly
Modern certificates are short-lived on purpose. Let's Encrypt certificates last 90 days and are designed to auto-renew, and the industry is moving toward even shorter lifespans. That's more secure, but it means renewal is a recurring automated job - and automated jobs fail quietly.
The classic outage is an auto-renewal that broke weeks ago (a changed DNS record, an expired API token, a moved webroot) and nobody noticed until the certificate lapsed. Periodically checking the days-remaining, or monitoring it, is how you avoid finding out from an angry recipient.
Frequently asked questions
What does an SSL certificate do?
It encrypts the connection between a browser and your server (HTTPS) and proves the domain's identity. An invalid or expired certificate triggers browser warnings and breaks secure links.
How often do SSL certificates expire?
It varies - Let's Encrypt certificates last 90 days and usually auto-renew, while commercial certificates often last a year. A failed auto-renewal is the most common cause of unexpected expiry.
What certificate details should I check?
The issuer (who signed it), the subject (which domain it covers - watch for www vs apex mismatches), the validity dates, and the days remaining. Under two weeks left is worth acting on.
Does SSL affect email authentication?
Not directly - SPF, DKIM and DMARC are separate. But your tracking links and landing pages run over HTTPS, so a broken certificate breaks click-through and erodes trust even when your email authenticates perfectly.
Why does SSL matter for cold email?
Your tracking links and landing pages run over HTTPS. A broken certificate makes links fail or throw security warnings, hurting click-through and making a legitimate campaign look untrustworthy.
Next steps
Stop configuring DNS by hand
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