A 496 SSL Certificate Required error is an nginx-specific code for: "This server requires you to present a valid client SSL certificate, but you didn't provide one.".

How do I fix or troubleshoot a 496 Error?

Common steps include reloading the page in your browser, checking for typos in the URL, verifying server status, clearing browser cache or cookies, and contacting the website owner or server administrator if the error persists.

496 Error | Error-Message.Net

A 496 SSL Certificate Required error is an internal status code used by nginx when a client attempts to connect to a location that requires mutual TLS authentication without providing a client certificate.

When ssl_verify_client on; or ssl_verify_client optional_no_ca; is configured in nginx, any client that fails to present a certificate during the TLS handshake is rejected with code 496.

Determining why

The website or API requires two-way SSL (mutual TLS) where both the server and the client must cryptographically identify themselves. Your browser or API client did not transmit a certificate during the TLS connection.

Steps you could possibly take:

Install your client certificate - Import your .pfx or .p12 client certificate into your operating system’s certificate store or browser settings.
If connecting via curl or an API client:
- Supply your certificate and private key using --cert cert.pem --key key.pem.
If you are the server administrator:
- Check your nginx configuration to ensure client verification is only enforced on routes where it is strictly intended.

Source: nginx Documentation - ngx_http_ssl_module