SSL Expiry Monitor

Why an SSL expiry monitor belongs in the admin routine

An SSL expiry monitor drags a dumb, common outage back into something boring and manageable, because a dead cert is a dumb way to take a site down and it happens constantly. Visitors hit a scary browser warning. API clients just refuse to connect. Half your embedded widgets break. And the support tickets land way before anyone figures out the cause is something as boring as an expired certificate. Here's the annoying part: it might have renewed fine last month and still fail this month. A DNS challenge broke. Somebody swapped a CDN hostname. A staging box got exposed. Or the person who owned renewals left and nobody's watching that account anymore.

A watchlist tackles that risk head on. Rather than poking at one domain whenever it crosses your mind, you keep the public hostnames in one place, run them all at once, and let the list sort itself so the nearest cliff is right at the top. That's useful for the main site and its www twin. It's even more useful for the stuff that quietly matters: dashboards, APIs, anything handling payments or logins, the odd client microsite, whatever tool subdomain people actually depend on.

What this on-demand monitor checks

• Whatever certificate is actually being served on port 443 for each host, right now.
• The validity dates, and how many days you've got left.
• Issuer and subject common-name hints, when the cert bothers to hand them over.
• Whether the hostname you typed lines up with a SAN entry or the subject name in the parsed summary. It usually does. Sometimes it really doesn't.
• A review date worked back from the threshold you picked.
• Anything that failed to connect or failed the cert check, which is the stuff you want to look at first.

How to choose a renewal threshold

Fourteen days is cutting it close. Honestly, that's barely a warning at all if something in your pipeline is broken. Thirty is the floor I'd suggest for a plain little site. Sixty feels saner once DNS validation, CDN edges, or three people who all think someone else owns renewals enter the picture, and that's where I usually land. Ninety is for teams who want the renewal work showing up on a board before a cert hits its last stretch. None of this is about panicking early. It's just buying yourself enough runway to fix the challenge path and retest the live hostnames without sweating.

A practical renewal workflow

1. Keep the list to hostnames real people or real integrations actually open. Don't pad it.
2. Run it before anything risky: a migration, a DNS change, a CDN swap, a release window.
3. Look at the soonest cert first. Then the outright failures. Then the hostname mismatches that aren't on fire but still smell wrong.
4. Before the final week, confirm auto-renew is alive, you own the DNS challenge, and there's a manual fallback if it all goes sideways.
5. Once it's renewed, rerun the exact public hostname. And if HTTPS started behaving differently, go poke at the headers or redirects.

Monitoring is more than one date

Expiry is the loud signal. The quieter stuff around it trips people up just as often. A cert with months left can still be flat-out wrong for a hostname you just added. A renewal can succeed on the origin while your CDN happily keeps serving the old one. And a wildcard covers one tier of subdomains while a deeper name sits outside it, completely uncovered. So keep both tools handy. Use this monitor for fast triage, and when one host looks off, open the certificate checker and actually read it.

Frequently asked questions