Understanding and Steps to Resolve
the 497 Error Code

Error code 497, "HTTP Request Sent to HTTPS Port," is specific to Nginx, an open-source web server. This error occurs when a client attempts to establish a connection using HTTP on a port that expects HTTPS. The server rejects the request because of this mismatch between protocols.

Understanding error 497 helps diagnose protocol mismatches and ensure proper configuration and enforcement of HTTPS connections in Nginx.

1.     Incorrect URL Protocol: Clients use HTTP instead of HTTPS, often due to outdated bookmarks or incorrect links.

2.     Server Configuration: The server is set up to handle HTTPS requests on specific ports, and an HTTP request is mistakenly sent to one of these ports.

3.     Manual Entry Errors: Users manually entering URLs may forget to use "https://" and default to "http://," causing the protocol mismatch.

1.     Secure Websites: Websites requiring secure connections will return a 497 error if accessed via HTTP on an HTTPS-configured port.

2.     API Endpoints: Secure APIs that only accept HTTPS requests will reject HTTP requests on designated secure ports, resulting in a 497 error.

3.     Enforcing HTTPS: Sites enforcing HTTPS for all traffic may encounter 497 errors if automatic redirection from HTTP to HTTPS is not implemented.

Error 497, "HTTP Request Sent to HTTPS Port," occurs when a client makes an HTTP request to a port configured for HTTPS traffic. Here’s how to diagnose and fix this issue effectively:

1.     Check URL Protocols: Ensure that all URLs use "https://" instead of "http://". Update any bookmarks, links, or references that incorrectly use HTTP.

2.     Configure Nginx Redirection:

• Set up automatic redirection from HTTP to HTTPS in your Nginx configuration to ensure that all HTTP requests are redirected to the correct protocol.

• Example configuration:

server {
    listen 80;
    server_name example.com;
    return 301 https://$host$request_uri;
}

server {
    listen 443 ssl;
    server_name example.com;
    ssl_certificate /path/to/certificate.crt;
    ssl_certificate_key /path/to/private.key;
    # Other HTTPS configurations
}

3.     Update Server Configuration: Ensure the server is configured correctly to handle HTTPS requests on the intended ports. Verify that SSL certificates are correctly installed and configured.

4.     Test the Configuration: After making changes, test the configuration by accessing the site using HTTP and HTTPS to confirm that HTTP requests are correctly redirected to HTTPS.

5.     Monitor and Log: Implement logging and monitoring to track instances of error 497. This can help identify patterns and ensure that redirection is functioning correctly.

Following these steps, you can resolve the 497 error, ensure that clients use the correct protocol, and enhance the security and reliability of your connections. Regular monitoring and proper configuration will help maintain seamless HTTPS enforcement.

Regularly checking web page statuses is essential for promptly identifying and addressing issues. The Atomseo Broken Link Checker facilitates this process by offering up to 1,500 free daily scans. This tool improves your website's performance by precisely identifying server errors, including the 497 status code.