How to Fix ssl_error_rx_record_too_long Firefox Error?

The SSL_ERROR_RX_RECORD_TOO_LONG error is a specific and often confusing browser error that impacts users when they try to access a website over HTTPS using Mozilla Firefox. The error is displayed with a message similar to:

“Secure Connection Failed.
An error occurred during a connection to [website].
SSL received a record that exceeded the maximum permissible length.
Error code: SSL_ERROR_RX_RECORD_TOO_LONG.”

This message appears because Firefox expects a secure SSL/TLS handshake when connecting to a website over HTTPS (usually on port 443), but instead receives data that doesn’t match the required protocol format. In most cases, that means Firefox is expecting encrypted data but is instead receiving either plain HTTP data or improperly configured TLS data.

Unlike generic errors such as “Your connection is not secure” or “SSL protocol error” that may appear in multiple browsers, this exact message—SSL_ERROR_RX_RECORD_TOO_LONG—is specific to Mozilla Firefox. However, the underlying issue may also trigger different errors in other browsers, such as ERR_SSL_PROTOCOL_ERROR in Google Chrome or generic “Connection reset” messages in Safari or Edge.

Despite its technical phrasing, this error almost always points to a server-side misconfiguration rather than a certificate issue. For example, a server might be configured to serve plain HTTP traffic through port 443 (the default port for HTTPS), or the SSL module on the server may not be responding with a proper TLS handshake. It can also occur if the server’s SSL context is not fully set up, if incompatible cipher suites are chosen, or if the server is not listening securely for HTTPS requests.

More technically, the phrase “record too long” suggests that the browser has received a response packet that does not match what a TLS “record” should look like. A TLS record has a strict byte format that the browser checks before even considering encryption, and when this validation fails, Firefox throws this error.

In short: Firefox is receiving the wrong kind of response over a secure connection, and this almost always means the remote server (not the browser) is misconfigured for SSL/TLS. While the error can occasionally be influenced by a user’s browser settings or network, the root issue typically lies with the website’s hosting/server configuration.

Common Causes of SSL_ERROR_RX_RECORD_TOO_LONG

The SSL_ERROR_RX_RECORD_TOO_LONG error in Firefox is most commonly triggered by a server-side configuration issue rather than a browser problem. While it may appear to be a certificate or encryption problem at first glance, it actually indicates that the server is not correctly handling the secure HTTPS connection request from Firefox. The browser expects encrypted SSL/TLS handshake data but receives something else—typically unencrypted or malformed data—instead.

This mismatch typically happens when the server is not properly configured to serve HTTPS traffic on port 443, which is the default SSL port. Below are the most frequent causes of this error:

1. Port 443 Listening to HTTP Instead of HTTPS

One of the most common reasons behind this error occurs when the server is configured to respond to HTTP requests on port 443 instead of handling HTTPS protocol. Since HTTPS requires SSL negotiation before sending any readable data, Firefox expects a valid TLS handshake. When it instead receives raw HTTP data, it sees that data as invalid and throws the SSL_ERROR_RX_RECORD_TOO_LONG error.

In simpler terms, this happens when the server is speaking “regular HTTP” when Firefox is expecting “secure HTTPS,” causing a protocol mismatch that breaks the connection.

2. SSL/TLS Not Properly Configured on the Server

If SSL/TLS is not enabled or properly configured on the server (for example, the SSL module is disabled on Apache or missing required certificates), Firefox cannot establish a secure connection. This often happens in cases where:

• The server admin installed a certificate but did not specify SSL in the VirtualHost configuration

• The server has multiple VirtualHost blocks and the one handling HTTPS lacks proper SSL directives

• The SSL certificate paths or key files are missing, misconfigured, or incorrect

In Apache, this may mean the <VirtualHost *:443> block is inactive or incomplete. In Nginx, it might mean that ssl on; or listen 443 ssl; is missing or misconfigured.

3. Outdated or Unsupported TLS or Cipher Suite Settings

The error can also occur when the server is configured with outdated or deprecated SSL/TLS versions (like SSLv3 or TLS 1.0) or when HTTPS is enabled without proper cipher suites and key exchange methods. Modern browsers—including Firefox—no longer support insecure protocols by default.

If a server only supports old SSL protocols and the browser attempts to initiate TLS 1.2 or TLS 1.3, the handshake fails immediately and may surface as SSL_ERROR_RX_RECORD_TOO_LONG in Firefox.

4. Server or CDN Sending Non-SSL Content Through HTTPS Port

The error may also appear when a misconfigured CDN, reverse proxy, or load balancer improperly forwards requests without SSL termination. For example, this is common when:

• Nginx proxies HTTP traffic to a backend that expects HTTPS

• Cloudflare or a similar service is set to “Flexible SSL” while the origin server runs only HTTP

• A firewall intercepts traffic and sends back HTML on a supposed “secure” port

In other words, even if a site appears to be https:// in the browser, the server or network in-between may be behaving as plain HTTP.

5. Shared Hosting or Multi-Domain Server Without Correct SNI Setup

On servers hosting multiple HTTPS websites on a single IP address, SNI (Server Name Indication) must be properly configured. If SNI is missing or incorrectly set, the server may not know which certificate to serve, causing Firefox to interpret the connection as invalid.

On shared hosting platforms or cPanel servers, users may see this error if their SSL certificate was installed but not correctly tied to the domain binding, or if the wrong IP or domain mapping is used.

These issues are almost always server-side misconfigurations, which is why simply refreshing the browser or trying another device does not fix the issue. The server must be configured to speak proper TLS over port 443, have a complete certificate chain installed, and use secure and matching SSL/TLS protocol versions.

Visitor-Side Troubleshooting (End Users)

If you are seeing the SSL_ERROR_RX_RECORD_TOO_LONG error in Firefox while trying to access a website, you may assume the problem lies with your browser or device. While this error is primarily caused by misconfiguration on the server hosting the website, there are situations in which the error may appear locally due to issues with browser settings, network proxies, outdated caches, or conflicting third-party tools.

Below are several steps you can take as a visitor to troubleshoot and potentially resolve the issue. These solutions are particularly helpful when the affected website works fine for other users, works in a different browser, or loads correctly on another device or network.

1. Clear Firefox Cache and SSL State

Firefox stores cached versions of visited pages and SSL certificate details. If the browser is holding onto an outdated version of the site or SSL data, it may fail to complete a proper handshake with the server, resulting in this error.

To fix this:

1. Open Firefox.

2. Go to Menu > Settings > Privacy & Security.

3. Scroll to “Cookies and Site Data” and click “Clear Data.”

4. Optionally, clear the “Cached Web Content” only.

5. Restart the browser and revisit the site.

Clearing the cache forces Firefox to request a fresh SSL handshake with the server, which can resolve outdated or cached certificate issues.

2. Disable Proxy or VPN (If Enabled)

A proxy server or VPN can interfere with how secure connections are routed to the website. Some proxies funnel HTTPS traffic through HTTP channels, confusing Firefox into thinking the server is responding using a non-SSL protocol, which can lead to the SSL_ERROR_RX_RECORD_TOO_LONG message.

To disable proxy in Firefox:

1. Go to Menu > Settings > General.

2. Scroll down to “Network Settings.”

3. Click “Settings…” and select “No proxy” or “Use system proxy settings.”

If you are using a VPN client, try disconnecting temporarily and refreshing the page. If the site loads correctly without the VPN, it’s likely that the VPN routing was stripping SSL or misrouting your request.

3. Try a Different Browser or Device

While this doesn’t fix the root cause, testing the site in Google Chrome, Safari, or Microsoft Edge can help you determine whether the issue is isolated to Firefox. If the site loads successfully in another browser, the problem may lie with how Firefox interprets the response during the SSL handshake.

If the error appears in multiple browsers, chances are high that the problem is on the server side, and only the website administrator can resolve it.

4. Update Firefox to the Latest Version

If you are using an outdated version of Firefox, it might not properly support updated TLS protocols or security standards that the server expects. Always ensure your browser is current:

1. Open Firefox and click Menu.

2. Go to Help > More troubleshooting information.

3. Click “Check for updates.”

Installing the latest patches ensures proper compatibility with modern HTTPS security standards such as TLS 1.3 and current cipher suites.

5. Contact the Website Owner

If you’ve tried all the troubleshooting steps and the error still appears, especially if it only affects a specific website, the best course of action is to notify the website owner or admin. Let them know you are getting the SSL_ERROR_RX_RECORD_TOO_LONG error so they can investigate and correct the server configuration.

Most visitors cannot fix server-side SSL errors—these must be resolved by the site’s hosting administrator.

These steps provide a complete checklist of what an end-user can do before concluding that this is not a browser problem at all but a server misconfiguration issue. In most cases, the ultimate fix lies with the website owner correcting their SSL/TLS configuration, but these visitor-side solutions help eliminate local causes and may resolve the issue if caused by caching, proxies, or outdated settings.

Admin & Webmaster Solution Guide

If you’re the owner or administrator of the website triggering the SSL_ERROR_RX_RECORD_TOO_LONG error in Firefox, the root cause almost always lies with your server’s SSL/TLS configuration. Unlike end-user troubleshooting, server-side fixes are technical and require access to your hosting control panel, server configuration files, or cloud provider dashboard.

The ultimate cause of this Firefox error is that the server is not correctly replying with a proper TLS handshake on the expected HTTPS port (443). In most cases, the server is either misconfigured to serve plain HTTP on port 443, or the SSL module/certificate has not been setup or enabled properly.

The following steps outline a complete resolution path for administrators, whether you’re using Apache, Nginx, IIS, or a cloud platform like AWS, cPanel, or DigitalOcean.

Step 1: Confirm the Server-Side Issue with Diagnostic Tools

Before making configuration changes, it’s important to validate what the server is currently doing.

Run the following command from a terminal (replacing yourdomain.com with your domain name):

If the result shows content like 400 Bad Request or if you see plain HTTP headers or HTML rather than SSL/TLS information, it means the server is not responding with a proper TLS handshake.

Similarly, you can use online SSL testing tools like SSL Labs, DigiCert, or DNSChecker to confirm whether the hostname is responding with valid SSL configuration. This will help determine whether:

• HTTPS is properly bound to port 443

• Correct certificates are being served

• Intermediate certificates are missing

• The server is responding with non-SSL data

Once you confirm this is a server issue, proceed to fix the configuration.

Step 2: Validate Port and Virtual Host Configuration

This error most commonly occurs when the server serves HTTP traffic on port 443 due to a missing or incorrect SSL virtual host configuration.

Apache Example:

In Apache, make sure your configuration file includes a proper SSL virtual host on port 443, such as:

Also ensure that the following lines exist to enable SSL and support HTTPS traffic:

After making changes, restart Apache:

Without a correctly defined <VirtualHost *:443> block, Apache may respond with HTTP instead of HTTPS, causing Firefox to reject the connection.

Nginx Example:

In Nginx, you’ll need to specify the correct server block for HTTPS:

If the listen 443 ssl; directive is missing, Nginx will default to plain TCP on port 443 rather than TLS, causing the SSL_ERROR_RX_RECORD_TOO_LONG issue in Firefox.

Apply changes with:

Step 3: Ensure SSL/TLS Module, Certificate, and Protocols Are Correct

Proper SSL/TLS configuration requires more than just pointing the server to a certificate file. You must also:

• Enable the SSL/TLS module (e.g., mod_ssl in Apache)

• Use valid certificate and key file paths

• Include intermediate certificates (fullchain)

• Configure compatible protocol versions and cipher suites

Outdated or insecure protocols like SSLv3, TLS 1.0, and TLS 1.1 should be disabled. Modern systems should support TLS 1.2 at a minimum, with TLS 1.3 if possible.

Example Apache SSL settings:

Example Nginx settings:

Certificate chains should also be properly installed. If you only install the domain certificate and not the intermediate chain, clients may reject the certificate, resulting in handshake failures or errors like this one.

Step 4: Check for Proxy, Load Balancer, or CDN Interference

If you’re using Cloudflare, AWS ALB, a reverse proxy, or some other SSL-terminating service, you must ensure SSL termination is set up correctly.

For example:

• In Cloudflare, set SSL mode to Full (strict), not Flexible, otherwise Cloudflare will connect to your origin via HTTP and cause this error.

• If using a load balancer, ensure it’s forwarding HTTPS traffic to your server correctly or handling termination with its own certificate.

• Check for firewalls dropping or rewriting inbound traffic on port 443.

These tools are often overlooked but can be a major cause of this error if not configured properly.

Step 5: Restart Services and Validate the Fix

Once you’ve applied all necessary changes:

1. Restart your web server (Apache, Nginx, IIS, etc.)

2. Clear browser and CDN caches (if applicable)

3. Re-run SSL testing (OpenSSL, SSL Labs)

4. Test in Firefox, Chrome, and other browsers

A working server should respond with a proper TLS handshake when tested on port 443. If Firefox no longer throws the SSL_ERROR_RX_RECORD_TOO_LONG error, the fix was successful.