ERR_QUIC_PROTOCOL_ERROR is a Google Chrome error that appears when a connection over QUIC, the transport protocol behind HTTP/3, fails. The page simply refuses to load, often on one site while everything else works, and often on one network while the same site loads fine on another. What makes this error worth understanding is that you […]
MOZILLA_PKIX_ERROR_SELF_SIGNED_CERT is one of the more precise error codes Firefox produces. It is not a general “something is wrong with this certificate” message. Firefox shows this exact code only after it has examined the certificate the server sent and established that the certificate signed itself, rather than being signed by a Certificate Authority the browser […]
DLG_FLAGS_SEC_CERT_CN_INVALID is a Windows error, not a browser error. It is produced by WinINet, the networking stack built for Internet Explorer, and it means the certificate a server presented does not cover the hostname that was requested. If you are looking at this code, the software in front of you is running on that legacy […]
HAProxy is a TCP and HTTP load balancer that terminates TLS, so it decrypts traffic at the edge and forwards plain HTTP to your backend servers. That makes it the only machine in the path that needs the certificate, and it wants that certificate in a specific shape: one file, holding the certificate, any intermediates, […]
In this section you will find our OpenSSL guides: installing OpenSSL on Windows and on Ubuntu, checking which version you are running, generating a self-signed certificate, and checking when a certificate expires. How to Install OpenSSL on Windows Windows does not include OpenSSL, so you have to install it yourself. This guide covers picking the […]
This guide shows you how to generate a CSR (Certificate Signing Request) on Windows using the tools that ship with the operating system. The CSR is a PKCS #10 text block that carries your public key and subject details to the Certificate Authority, which signs it and returns your SSL/TLS certificate. The matching private key […]
A site that loaded fine yesterday now throws a certificate warning. Or you picked the wrong certificate at a smart card prompt and the browser will not ask again. Clearing the SSL state is the standard advice for both, and it does work, but only if you clear the cache that actually holds the stale […]
SSL certificates have limited validity periods and must be renewed regularly to stay trusted by browsers. Public certificates issued after March 15, 2026 are limited to 200 days, with the maximum validity dropping to 100 days on March 15, 2027 and 47 days on March 15, 2029. Knowing exactly when a certificate expires helps you […]
A self-signed certificate is one you issue to yourself instead of buying it from a certificate authority. Browsers won’t trust it automatically, so it has no place on a public website, but it is the fastest way to put HTTPS on a development machine, a staging box, an internal dashboard, or any service that never […]
An SSL error on an iPhone means iOS refused to open an encrypted connection to a website or to an app’s server. Safari usually reports it as This Connection Is Not Private, while apps tend to fail with a shorter complaint about a secure connection that could not be made. Sometimes the problem really is […]
