How to Check a Website SSL Certificate

Every time a user submits a password or payment detail on a website, an encrypted tunnel forms between their browser and the server. An SSL/TLS certificate both creates that tunnel and proves the server is genuinely who it claims to be. Without it, data travels in plain text — readable by anyone along the route.

What SSL/TLS Is and Why HTTPS Matters

SSL (Secure Sockets Layer) is the legacy name; today's standard is TLS (Transport Layer Security), specifically versions 1.2 and 1.3. Browsers still say "SSL" but mean TLS. When a connection is secured, the address bar shows HTTPS and a padlock icon, guaranteeing three things: traffic encryption, data integrity, and server authentication.

If the padlock is missing — or the browser shows a "Your connection is not private" warning — visitors will almost certainly leave. Search engines react too: Google officially lists HTTPS as a ranking signal, meaning an unsecured site is penalised before a single user even lands on it.

What an SSL Certificate Check Actually Shows You

Running an SSL certificate check opens the site's digital passport and returns several critical fields.

• Issuer (CA) — the Certificate Authority that signed the cert: Let's Encrypt, DigiCert, Sectigo, etc.
• Validity period — exact issue and expiry dates.
• Days remaining — the most actionable number; fewer than 14 days means imminent risk of a browser block.
• SAN domains (Subject Alternative Names) — every domain and subdomain the certificate covers.
• Signature algorithm and key length — RSA 2048+ or ECDSA 256 are considered safe; anything older is not.

DV, OV, and EV Certificates: What the Difference Means

Certificates are not all equal. They differ in how thoroughly the issuing authority verifies the owner's identity. The table below summarises the three main types.

Why an Expired or Self-Signed Certificate Is Dangerous

An expired certificate is not just technical debt — it is a hard blocker. Chrome, Firefox, and Safari immediately serve a full-page warning that most users will not bypass. A self-signed certificate (issued by the server itself rather than a trusted CA) triggers the same wall: the browser cannot verify the server's identity, so it treats the connection as potentially hostile.

"Studies consistently show that the large majority of users who encounter a browser security warning abandon the site immediately — and rarely return. Trust takes months to rebuild and seconds to lose."

Beyond user trust, a broken certificate directly affects search visibility. Googlebot crawls HTTPS sites preferentially, and pages served with certificate errors can be dropped from the index entirely. For e-commerce or any site with logins, that translates into measurable revenue loss.

Four Warning Signs to Check Right Now

A quick audit takes under a minute. Watch for these red flags.

1. The certificate expires in fewer than 30 days — schedule renewal immediately.
2. The certificate is issued to a different domain (Common Name or SAN mismatch).
3. The server still supports TLS 1.0 or 1.1 — modern browsers block these legacy versions.
4. The certificate chain is incomplete — an intermediate CA is missing from the server configuration.

You can verify all of the above in one click with the SSL certificate check tool, or explore the full website analysis toolkit for additional diagnostics.

The takeaway is straightforward: SSL is not optional — it is the baseline of any credible online presence. A thirty-second check today can prevent hours of damage control tomorrow.

SSL and SEO: how the certificate affects rankings

HTTPS is no longer just a security checkbox — it's a ranking factor and a driver of behavioural metrics.

• Direct ranking signal. All else being equal, an HTTPS site has a slight edge over HTTP — the official position of search engines.
• Behavioural factors. A browser warning sharply raises bounce rate: the visitor leaves before the page loads, and the engine records a poor signal.
• Indexing. Certificate errors stop crawlers from reaching pages, and some content can drop out of the index.

Related technical checks are the page speed and HTTP headers tools.

Frequently asked questions

How often should I check the certificate?

For a live site, once a month — better still, set up auto-renewal (Let's Encrypt has it built in). Check separately after moving hosts or changing domains. A quick manual check takes seconds with the SSL check, and the domain's own expiry via the domain expiry tool.

Is a free Let's Encrypt certificate worse than a paid one?

Not in encryption — the protection is identical. The difference is the validation type: paid OV/EV certificates also confirm the organisation, which matters for banks and large stores. For most sites a free DV certificate is enough.

What should I do if the certificate has already expired?

Issue and install a new one immediately — until then, browsers show visitors a warning page. If you use Let's Encrypt, check why auto-renewal failed (usually a stopped web server or changed DNS records, which you can inspect with the DNS check).

From the field

"A store lost orders for a week without knowing why — after a host migration the auto-renewal had silently broken, and half of all browsers were showing a warning. Now I run the domain through the checker once a month: a minute of work versus a week of losses."

That's exactly why it pays to read reviews in the Hosting & IT category before buying hosting: reliable providers set up SSL and auto-renewal for you.

Key takeaways

• An SSL certificate encrypts data and proves the site's identity; without it you get plain HTTP and a browser warning.
• The key fields to check are the issuer, the validity dates, and the days remaining.
• An expired or self-signed certificate scares off visitors and hurts search rankings.
• Check the certificate at least monthly and enable auto-renewal.