SSL Certificate Errors: What They Mean & How to Fix Them

What an SSL certificate error means

When you visit a site over HTTPS, your browser checks the site's SSL/TLS certificate before it encrypts anything. If that check fails, the browser can't be sure the site is the one you meant to reach, so it stops and shows a warning. The certificate might be expired, issued for a different name, signed by an authority the browser doesn't trust, or missing a link in its chain. Each failure has its own message, and each has a known fix.

Every SSL certificate error, explained

Here are the common ones, what each means, and where to find the full fix.

Your connection is not private (Chrome and Safari)

The most common SSL error. Chrome shows "Your connection is not private" and Safari shows "This Connection Is Not Private" when the browser can't verify the certificate, for any of the reasons below. Start here if the error doesn't name a specific code.

How to fix "your connection is not private"

NET::ERR_CERT_DATE_INVALID (certificate expired)

The certificate has expired, or isn't valid yet. Every certificate has a validity period, and once it passes, browsers stop trusting it. This one is also the easiest to prevent.

What a certificate's expiry date means

NET::ERR_CERT_COMMON_NAME_INVALID (name mismatch)

The certificate was issued for a different hostname than the one you're visiting. A certificate for example.com doesn't automatically cover www.example.com, and a single-name certificate doesn't cover a different subdomain.

What a certificate's common name is

NET::ERR_CERT_AUTHORITY_INVALID (untrusted authority)

The certificate was signed by an authority the browser doesn't trust. This is common with self-signed certificates, which work for testing but aren't trusted on the public web.

Self-signed certificates explained

Cloudflare Error 525 (SSL handshake failed)

Cloudflare couldn't complete the TLS handshake with your origin server. Usually the origin certificate, the SSL mode, or port 443.

How to fix Cloudflare Error 525

Cloudflare Error 526 (invalid SSL certificate)

Cloudflare reached your origin but couldn't validate its certificate, so it won't serve the site over HTTPS.

How to fix Cloudflare Error 526

Missing intermediate certificate

The browser can't build the full chain from your certificate back to a trusted root because an intermediate certificate is missing, so it treats the certificate as unverified.

How to fix a missing intermediate certificate

Why SSL certificate errors happen

Almost every SSL certificate error comes down to one of a handful of causes:

• The certificate has expired, or the server's clock is wrong and makes a valid certificate look expired.
• The certificate is self-signed, or issued by an authority the browser doesn't trust.
• The certificate doesn't match the domain you're visiting.
• The certificate chain is incomplete, so the browser can't verify it back to a trusted root.

How to fix an SSL certificate error

If the site is yours, the fix is almost always on the server: check the expiry date, renew or replace the certificate, make sure the name matches, and install the full chain. You can see exactly what a certificate is presenting with an openssl command before you change anything.

How to check a certificate with OpenSSL

If you're a visitor on someone else's site, the problem is theirs to fix. You can usually click through and proceed, but only on a site you know and trust, and never enter passwords or card details.

Stop certificate errors happening again

Certificate errors are almost always avoidable. Certificates expire on a schedule, so the only question is whether someone is watching the dates. SSL monitoring tracks every certificate and tells you before one expires, and a reminder email means this page is one you never have to come back to.

FAQ

Is an SSL certificate error dangerous?

It means your browser can't verify the connection is private. On a site you don't trust, treat it as a warning and don't enter passwords or card details.

Can I bypass an SSL certificate error?

Usually you can click "Advanced" and proceed. Only do that on a site you know and trust, and never enter sensitive information.

Why does my site show an SSL certificate error?

Usually an expired certificate, a name mismatch, or a missing intermediate certificate. Work through the causes above.

What's the difference between "not secure" and an SSL certificate error?

"Not secure" usually flags a site served over plain HTTP or with mixed content. An SSL certificate error is the stronger warning that the certificate itself can't be verified.