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Synthetic monitoring response codes

Synthetic monitors returns a number of additional response codes beyond standard HTTP response codes, visible in the Resources page. These response codes are based on Chromium's response codes and give you more detail on the behavior of your monitors.

Response codes

Synthetic monitoring returns the following additional response codes:

Response Code



net::ERR_FAILED, "Generic network error"


net::ERR_TIMED_OUT, "Timed out"


net::ERR_ACCESS_DENIED, "Access denied"




net::ERR_CONNECTION_CLOSED, "Connection was closed (TCP FIN)"


net::ERR_CONNECTION_RESET, "Connection was reset (TCP RST)"


net::ERR_CONNECTION_REFUSED, "Connection was refused"


net::ERR_CONNECTION_ABORTED, "Connection was aborted (no ACK received)"


net::ERR_CONNECTION_FAILED, "Connection attempt failed"


net::ERR_NAME_NOT_RESOLVED, "Host name could not be resolved"


net::ERR_INTERNET_DISCONNECTED, "Internet connection lost"


net::ERR_SSL_PROTOCOL_ERROR, "SSL protocol error"


net::ERR_ADDRESS_INVALID, "Invalid IP address and/or port number"


net::ERR_ADDRESS_UNREACHABLE, "Unreachable IP address"


net::ERR_SSL_CLIENT_AUTH_CERT_NEEDED, "Server requested a client certificate for SSL client authentication"


net::ERR_NO_SSL_VERSIONS_ENABLED, "No SSL protocol versions are enabled"


net::ERR_SSL_VERSION_OR_CIPHER_MISMATCH, "Client and server don't support a common SSL protocol version or cipher suite"


net::ERR_SSL_RENEGOTIATION_REQUESTED, "Server requested a renegotiation (re-handshake)"


net::ERR_CERT_ERROR_IN_SSL_RENEGOTIATION, "During SSL renegotiation (re-handshake), the server sent a certificate with an error"


net::ERR_BAD_SSL_CLIENT_AUTH_CERT, "SSL handshake failed because of a bad or missing client certificate"




net::ERR_SSL_NO_RENEGOTIATION, "Peer sent an SSL no_renegotiation alert message"


net::ERR_ACCESS_DENIED, "Access denied"


net::ERR_SSL_CLIENT_AUTH_SIGNATURE_FAILED, "Unable to sign the CertificateVerify data of an SSL client auth handshake with the client certificate's private key"


net::ERR_WS_PROTOCOL_ERROR, "WebSocket protocol error - connection terminated due to a malformed frame or other protocol violation"


net::ERR_ADDRESS_IN_USE, "Failed to bind to an address because already in use"


net::ERR_SSL_HANDSHAKE_NOT_COMPLETED, "SSL handshake has not completed"


net::ERR_SSL_BAD_PEER_PUBLIC_KEY, "SSL peer's public key is invalid"


net::ERR_SSL_PINNED_KEY_NOT_IN_CERT_CHAIN, "Certificate didn't match built-in public key pins for the host name"


net::ERR_CLIENT_AUTH_CERT_TYPE_UNSUPPORTED, "Server request for client certificate did not contain any types we support"


net::ERR_ORIGIN_BOUND_CERT_GENERATION_TYPE_MISMATCH, "Server requested one type of cert, then requested a different type while the first was still being generated"


net::ERR_SSL_DECRYPT_ERROR_ALERT, "SSL peer sent us a fatal decrypt_error alert"


net::ERR_SSL_SERVER_CERT_CHANGED, "SSL server certificate changed in a renegotiation"


net::ERR_SSL_INAPPROPRIATE_FALLBACK, "SSL server indicated that an unnecessary TLS version fallback was performed"


net::ERR_CT_NO_SCTS_VERIFIED_OK, "All Signed Certificate Timestamps failed to verify"


net::ERR_SSL_UNRECOGNIZED_NAME_ALERT, "SSL server sent us a fatal unrecognized_name alert"


net::ERR_SSL_CLIENT_AUTH_CERT_BAD_FORMAT, "Failed to import a client certificate from the platform store into the SSL library"


net::ERR_SSL_FALLBACK_BEYOND_MINIMUM_VERSION", "SSL server requires falling back to a version older than the configured minimum fallback version"


net::ERR_ICANN_NAME_COLLISION", "Resolving a hostname to an IP address list included the IPv4 address \"\". This is a special IP address which ICANN has recommended to indicate there was a name collision, and alert admins to a potential problem"


net::ERR_CERT_COMMON_NAME_INVALID, "Server responded with a certificate whose common name did not match the host name"


net::ERR_CERT_DATE_INVALID", "Server responded with a certificate that is either expired or not valid yet"


net::ERR_CERT_AUTHORITY_INVALID, "Server responsde with a certificate signed by an untrusted authority"


net::ERR_CERT_CONTAINS_ERRORS", "Server responded with a certificate that contains errors"


net::ERR_CERT_NO_REVOCATION_MECHANISM, "Certificate has no mechanism for determining if it is revoked"


net::ERR_CERT_UNABLE_TO_CHECK_REVOCATION", "Revocation information for the security certificate for this site is not available"


net::ERR_CERT_REVOKED, "Server responded with a certificate that has been revoked"


net::ERR_CERT_INVALID, "Server responded with a certificate that is invalid"


net::ERR_CERT_WEAK_SIGNATURE_ALGORITHM, "server responded with a certificate that is signed using a weak signature algorithm"


net::ERR_CERT_NON_UNIQUE_NAME, "Host name specified in the certificate is not unique"


net::ERR_CERT_WEAK_KEY, "Server responded with a certificate that contains a weak key"


net::ERR_CERT_NAME_CONSTRAINT_VIOLATION, "Certificate claimed DNS names that are in violation of name constraints"


net::ERR_CERT_VALIDITY_TOO_LONG, "Certificate's validity period is too long"


net::ERR_EMPTY_RESPONSE, "Server closed the connection without sending any data"


net::ERR_DNS_TIMED_OUT, "DNS lookup timed out"


"unknown error, error not mapped"

For more help

Additional documentation resources include:

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