Firefox blocks a page with SEC_ERROR_UNKNOWN_ISSUER when it cannot work out who issued the certificate a site presented, or cannot connect that issuer back to a root certificate it trusts. The certificate itself is often perfectly valid: issued by a real Certificate Authority, matching the domain, and nowhere near its expiry date. What failed is […]
When Firefox blocks a page with a Secure Connection Failed screen and the code SSL_ERROR_RX_RECORD_TOO_LONG, the wording sends most people looking in the wrong direction. The message describes what Firefox measured, not what went wrong. Firefox is reporting that the data arriving from the server does not have the shape of a TLS record, and […]
NET::ERR_SSL_PINNED_KEY_NOT_IN_CERT_CHAIN is one of the few Chrome errors that almost nobody sees for the reason the internet says they see it. Most guides describe it as a site owner’s configuration mistake, something you caused by pinning the wrong key and can undo by reinstalling your certificate. That has not been true for years. The error […]
An SSL connection error on Android usually looks like a full-page warning that says “Your connection is not private,” and it can appear in Chrome, inside an app’s built-in browser, or as a silent failure in a native app that simply refuses to load anything. The message is generic on purpose, so it tells you […]
Mixed content is the odd one out among SSL problems. There is no warning page to click through, no error code to search for, and nothing wrong with your certificate. The page loads, the address bar looks normal, and yet something on it is missing: a logo that will not appear, a slider that never […]
Cloudflare’s error 525, “SSL Handshake Failed,” is one of the more confusing SSL errors to land on. The page your visitors get looks broken, yet your own server can appear perfectly healthy when you check it. The error is more specific than it first seems: it means Cloudflare reached your site’s network but could not […]
NET::ERR_CERT_COMMON_NAME_INVALID is named after a certificate field that Chrome stopped reading in 2017. The error still means what its name suggests, that the certificate a server presented was issued for a different hostname than the one in the address bar, but the field Chrome compares is no longer the Common Name. It is the subjectAltName […]
Most SSL connection errors give you something to try. This one does not. When Chrome shows NET::ERR_CERTIFICATE_TRANSPARENCY_REQUIRED, the connection was refused because of what the site’s certificate contains, or rather what it fails to contain, and none of the usual visitor-side fixes take part in that decision. This guide explains what the error actually checks, […]
Most certificate problems announce themselves. This one does not. When an intermediate certificate in your chain expires, your own certificate stays valid, your monitoring stays green, and the site keeps loading perfectly on the machine you check it from. Meanwhile some share of your visitors cannot reach you at all, and the ones who can […]
You open a site in Google Chrome and get a blank error page instead: “This site can’t provide a secure connection”, followed by the code ERR_SSL_PROTOCOL_ERROR. Microsoft Edge and the other Chromium browsers show the same message, because they share the same networking code. Most of the advice written about this code points in the […]
