SSL checker

An SSL checker answers one question quickly: will a browser, a phone and an API client all trust this certificate right now? Enter a domain above and the check opens a live TLS connection to the host, reads the certificate it is actually served, and reports the issuer, the validity window, the days remaining, the protocol versions offered and whether the chain is complete.

Why the chain matters more than the expiry date

Most people check certificates the way they check milk — is it out of date? Expiry is the easy failure, and it is the one monitoring catches. The quieter failure is an incomplete chain. Desktop browsers cache intermediate certificates from other sites they have visited, so a site with a missing intermediate looks perfectly fine on your laptop and fails on a fresh Android phone, on curl, on a payment gateway callback and inside anything that ships its own trust store. The site owner sees a padlock. Their customers see a warning. This check walks the chain from leaf to root so you see the gap your own browser is hiding.

What a good result looks like

A healthy host serves a leaf certificate that covers the exact hostname you typed, presents every intermediate needed to reach a trusted root, offers TLS 1.2 and TLS 1.3, and has comfortably more than a month left. A certificate that is valid but expires in nine days is not a pass — it is a deadline. Automated renewal fails more often than teams expect, usually because a validation path changed, a cron stopped running, or the certificate was reissued somewhere the renewal script no longer touches.

Common causes of a failed SSL check

A certificate issued for the apex domain but served on the www host, or the reverse. A load balancer updated while one node kept the old certificate. A renewal that completed at the certificate authority but was never deployed to the server. A wildcard that covers one level of subdomain and not two. Each of these produces the same red padlock for a visitor and each is invisible until someone looks.

From one check to continuous checking

Running this by hand tells you the state of one host at one moment. Certificates fail at the moment nobody is looking — a ninety-day certificate that renewed fine eleven times will eventually miss the twelfth. Continuous SSL monitoring runs the same handshake on a schedule and warns you well before the date, which is the difference between a calendar reminder and an outage.