SSL_ERROR_RX_RECORD_TOO_LONG: Non-TLS Response

SSL_ERROR_RX_RECORD_TOO_LONG means Firefox expected TLS but received HTTP or other plain text. 90% of cases: server is listening on port 443 as HTTP (not HTTPS). Check your nginx/apache config: port 443 needs ssl_certificate and listen 443 ssl.

The error can appear in Chrome, Edge, Opera, Brave (all Chromium-based), and partially in Firefox and Safari. Different browsers display the same code differently, but the underlying issue is the same.

1. Check the SSL certificate online — the Enterno.io checker shows the grade, expiry, chain, and specific cause.
2. If the issue is server-side — reissue the certificate via certbot or your chosen CA.
3. Update nginx/apache config (enable TLS 1.2/1.3, fullchain, correct ciphers).
4. Check kernel OpenSSL — an outdated openssl < 1.1 can break handshakes.
5. After deploy: recheck via SSL checker + clear the browser SSL cache.

Check SSL now →

• NET::ERR_CERT_AUTHORITY_INVALID
• ERR_CERT_DATE_INVALID
• ERR_SSL_PROTOCOL_ERROR
• Mixed Content
• Check SSL certificate online →

The SSL_ERROR_RX_RECORD_TOO_LONG error usually indicates an issue with your SSL configuration or a miscommunication between the client and server. To resolve it, ensure that your server is configured to use the correct SSL port (typically port 443), verify that your SSL certificate is correctly installed and valid, and check for any misconfigurations in your web server settings.

The SSL_ERROR_RX_RECORD_TOO_LONG error is a common issue encountered when establishing a secure connection over HTTPS. This error generally occurs when the server fails to properly handle the SSL handshake, leading to a situation where the client receives an unexpected response. Here are the primary causes of this error:

• Incorrect Port Configuration: SSL connections must be made over port 443. If your server is configured to handle HTTPS traffic on a different port, this error may occur.
• Misconfigured Web Server: If your web server is not set up correctly to serve SSL certificates, it may send back plain HTTP responses instead of the expected SSL handshake.
• Invalid SSL Certificate: An expired or improperly installed SSL certificate can also lead to this error, as the server cannot establish a secure connection.
• Firewall or Proxy Issues: Sometimes, a firewall or proxy may interfere with SSL traffic, causing the error to appear.

To effectively troubleshoot and resolve the SSL_ERROR_RX_RECORD_TOO_LONG error, it is essential to systematically check each of these potential causes.

To fix the SSL_ERROR_RX_RECORD_TOO_LONG error, follow these practical steps:

1. Check Server Configuration: Ensure that your server is listening on the correct port for HTTPS. Use the following command to check which services are running on port 443:

sudo netstat -tuln | grep :443

If you do not see your web server (e.g., Apache, Nginx) listening on port 443, you will need to configure it accordingly.

1. Verify SSL Certificate Installation: Make sure your SSL certificate is installed correctly. For Apache, you can check the configuration file (usually located in /etc/httpd/conf.d/ or /etc/apache2/sites-available/) to ensure that the SSLCertificateFile and SSLCertificateKeyFile directives point to the correct certificate files:

SSLCertificateFile /etc/ssl/certs/your_cert.crt
SSLCertificateKeyFile /etc/ssl/private/your_private.key

After making changes, restart your web server:

sudo systemctl restart apache2

1. Check for Mixed Content: Ensure that your website is not trying to load resources over HTTP when accessed via HTTPS. Use browser developer tools to identify any mixed content issues.
2. Test Your SSL Configuration: Utilize online tools like SSL Labs' SSL Test to verify your SSL configuration. This tool will provide detailed feedback on any issues related to your SSL setup.
3. Review Firewall Rules: If you're using a firewall, ensure that it allows traffic on port 443. You can list your firewall rules using:

sudo ufw status

Make sure that HTTPS traffic is allowed. If not, add a rule:

sudo ufw allow 'Nginx Full'

or

sudo ufw allow 'Apache Full'

By following these steps, you should be able to diagnose and resolve the SSL_ERROR_RX_RECORD_TOO_LONG error effectively.