NET::ERR_CERT_WEAK_SIGNATURE_ALGORITHM means the browser rejected the website certificate because it was signed with a cryptographic algorithm that is no longer considered secure. In practice, this usually points to legacy certificates that still rely on SHA-1 or similarly outdated signing methods that modern browsers distrust. :contentReference[oaicite:0]{index=0} This is not a cosmetic warning. It is a certificate
An HSTS error means the browser must use HTTPS, but the secure connection or certificate is broken HSTS error usually appears when a browser is forced to use HTTPS for a website, but the site’s certificate or secure connection is broken. HSTS stands for HTTP Strict Transport Security, a policy that tells browsers to connect
SEC_ERROR_UNKNOWN_ISSUER means Firefox does not trust the certificate issuer presented by the website. In plain language, Firefox cannot build a trusted certificate chain from the website certificate back to a known, trusted root certificate, so it blocks the connection as a security risk. :contentReference[oaicite:0]{index=0} This error is common on sites with broken certificate chains, self-signed
PR_END_OF_FILE_ERROR is a Firefox-specific secure connection error. It usually appears when Firefox cannot complete the HTTPS connection because something on the path interrupts or breaks the TLS handshake before a trusted secure session is established. This error is common on sites that otherwise work in Chrome or Edge, which makes it confusing. In real cases,
ERR_SSL_KEY_USAGE_INCOMPATIBLE means the browser received a certificate whose key usage settings do not fit the way that certificate is being used for HTTPS. In most cases, the certificate is real and the hostname may even be correct, but the certificate extensions are wrong for modern TLS. This error is especially common on internal websites, self-signed
SSL_ERROR_BAD_CERT_DOMAIN appears when the certificate does not match the domain name in the address bar SSL_ERROR_BAD_CERT_DOMAIN means the website is presenting an SSL certificate that does not match the domain name you opened. In practice, the browser asked for one hostname, but the server responded with a certificate issued for a different one. This error
NET::ERR_CERT_DATE_INVALID means the certificate looks expired, not yet valid, or the device clock is wrong NET::ERR_CERT_DATE_INVALID means the browser thinks the website’s SSL certificate is outside its valid date range. In plain terms, the certificate looks expired, not yet valid, or the device checking it has the wrong date, time, or time zone. This error
The “Your connection is not private” warning means the browser cannot verify the website’s HTTPS certificate Your Connection Is Not Private means the browser cannot trust the website’s HTTPS certificate or the secure connection in front of it. The problem can come from the website’s server, or locally from your device, network, antivirus, VPN, or
ERR_CERT_COMMON_NAME_INVALID means the certificate does not match the hostname in the address bar ERR_CERT_COMMON_NAME_INVALID means the SSL certificate presented by the website does not match the hostname in the browser address bar. In simple terms, the browser asked for one domain, but the server replied with a certificate for a different name. This error is
ERR_SSL_VERSION_OR_CIPHER_MISMATCH means the browser could not negotiate a secure HTTPS connection with the website. In most real cases, the cause is not random. It is usually a broken TLS setup, an invalid certificate assignment, an unsupported protocol version, or a mismatch between the server, CDN, and browser. This guide explains how to fix ERR_SSL_VERSION_OR_CIPHER_MISMATCH from