SSL Certificate Checker

An expired or misconfigured SSL certificate breaks trust instantly — browsers throw warnings and visitors flee. This checker analyzes a domain's certificate and TLS setup through the respected SSL Labs service, returning an overall security grade plus the certificate's issuer, validity dates, and how many days remain before it expires.

Site owners use it to catch a certificate before it lapses, developers verify a new deployment's HTTPS, and security-minded users check that a site is properly protected. The letter grade gives an at-a-glance verdict, while the expiry countdown — color-coded as it approaches — is the detail that prevents the dreaded surprise outage.

Because the analysis is performed by the SSL Labs API, the domain you check is sent to that service, and a fresh scan can take a few moments to complete.

The hostname you enter is submitted to the Qualys SSL Labs API, which performs a thorough server-side analysis of the site's TLS configuration and returns the results. This is a genuine third-party request — the hostname is sent to Qualys, and their servers connect to the site rather than your browser doing so.

A browser could not do this work itself. Inspecting a certificate chain, enumerating supported protocol versions and cipher suites, and testing for known vulnerabilities all require control over the handshake that no web page has.

Analysis takes time, since it involves many handshakes against the target, and results may be cached from a recent scan of the same host.

Expiry is the most common failure and the most avoidable. Certificates are short-lived by design now — ninety days for Let's Encrypt, and the industry is moving shorter still — which makes automated renewal essential rather than optional. A calendar reminder is not a strategy, and a lapsed certificate produces a full-page browser warning that stops visitors dead.

An incomplete chain is the second most common, and the most confusing to diagnose, because it often works in browsers while failing elsewhere. Browsers frequently cache intermediate certificates from previous sites and paper over the gap; command-line tools, mobile apps, and other clients do not. A site that works for you and fails for others is very often this.

Beyond validity, configuration matters: old protocol versions should be disabled, since TLS 1.0 and 1.1 are deprecated and SSLv3 long broken, and weak cipher suites should be removed. Note also that a valid certificate proves only that the connection is encrypted and the domain is what it claims — it says nothing about whether the site is trustworthy, which is why the padlock was never a safety indicator and browsers have de-emphasised it.