How to FIX SSL_Error_rx_Record_too_long in Firefox

Solution 1: Try to reset Firefox browser

The good solution to avoid using unwanted browser programs is resetting Firefox to default settings.

1. Type 'about:support' in the address bar;
2. You will see a troubleshooting window now;
3. Click on Refresh Firefox button and confirm the refresh;
4. Move to the next solution if that one doesn't help.

Solution 2: Try to update Firefox

1. Click to Open Menu > Help > About
2. The new window would show is your Firefox browser is up to date or update requires.
3. Click on 'Restart to update Firefox' is the update is available.
4. Reload the problematic website after update to check if the error is solved.
5. Move to the next solution if still same issue.

Solution 3: Try Disabling Browser Extensions

There are hundreds of extensions and some may block/affect your connection. Try to disable them to fix the issue.

1. Go to Open Menu -> Add-Ons;
2. Beside each extension, you will see the Disable button that you need to click for all extensions.
3. Restart the browser and retry opening the website.

Avoid next solutions!

1. Try to NOT bypass the security protocol by replacing the URL with the HTTP:// instead of HTTPS://. That is not a safe solution, as starting at 2018 it is standard to use secured connection for all websites.
2. Do not turn off your Anti-virus, that is a really bad idea. It is duty of webmaster to setup website properly, not yours to avoid problems.

Conclusions to summarize

1. For website owners. Check your server configuration. Check your SSL certificate and server with SSL Labs online tests, as maybe you need to use a proper and professional SSL certificate.
2. For website visitors. Avoid using the website if error not solved even after listed solutions. It is unsafe to use sites like that, the best what you can do is to contact webmasters / site owners and let them fix it.