Software & Apps Windows The SSL_ERROR_NO_CYPHER_OVERLAP Error: What It Is and How to Fix It How to stop Firefox from blocking every website by Gabriel Moss Writer Gabriel Moss has been writing about technology since 2017. His work has appeared in IGN, Road to VR, Fanbyte, UploadVR, VRScout, VR Fitness Insider, and more. our editorial process LinkedIn Gabriel Moss Updated on January 24, 2020 Windows The Ultimate Laptop Buying Guide Tweet Share Email SSL_ERROR_NO_CYPHER_OVERLAP is the name of an error that occurs when Firefox fails to get the proper security information from a website you’re attempting to connect to. How the Firefox SSL_ERROR_NO_CYPHER_OVERLAP Appears Unsplash This SSL_ERROR_NO_CYPHER_OVERLAP error can appear when you connect to an older website that lacks updated security credentials, thus the acronym SSL, which stands for Secure Sockets Layer. Secure Sockets Layer refers to encryption between your computer and an internet server, but if your Firefox browser is running into errors connecting to multiple sites, there may be a local issue. You’ll know that you’ve run into SSL_ERROR_NO_CYPHER_OVERLAP when you see an error message that says: An error occurred during a connection to (IP address name). Cannot communicate securely with peer: no common encryption algorithm(s). Error code: SSL_ERROR_NO_CYPHER_OVERLAP. You will also see a tip that explains the “authenticity of the received data cannot be verified,” and to contact the owner(s) of the website to inform them of this. Granted, it may not be a website issue at all––the error code will also appear if your version of Firefox is misconfigured or out of date. Cause of the SSL_ERROR_NO_CYPHER_OVERLAP Firefox Error Aside from a website potentially experiencing server-side SSL issues, it’s possible your Firefox settings are causing a miscommunication between the website server and your computer. This is a far likelier case if many different websites are throwing the error code SSL_ERROR_NO_CYPHER_OVERLAP. You should always keep Firefox up to date anyhow, but an outdated version of Firefox is a potential cause of Firefox error SSL_ERROR_NO_CYPHER_OVERLAP appearing. If either TLS or SSL3 are disabled or otherwise misconfigured in your Firefox TLS settings, the error code will also commonly spring up. Finally, any website that uses RC4 (Rivest Cipher 4) in its encryption will run into issues with Firefox TLS no matter what. This is because RC4 was prohibited from TLS in 2015. How to Fix SSL_ERROR_NO_CYPHER_OVERLAP If this error has appeared, here are somethings you can do to fix it and get back to browsing: Update Firefox. You should always keep Firefox up to date anyhow, but an outdated version of Firefox is a potential cause of Firefox error SSL_ERROR_NO_CYPHER_OVERLAP appearing. Force Firefox TLS settings to 1.3. Open a new tab and type about:config into the URL bar. If Firefox directs you to a warning page, select Accept the Risk and Continue. When you land on the Advanced Preferences page, type tls into the search bar underneath the regular Firefox URL bar. In the results, you’re looking for security.tls.version.max, which should be set to 4 under normal circumstances. If it’s set to something else, select the pencil icon to the far right of security.tls.version.max and change the number to 4. Loosen Firefox encryption protocol. Another way to stop Firefox error code SSL_ERROR_NO_CYPHER_OVERLAP is by disabling the protection that blocks Firefox from accessing websites that it deems unsafe. To do this, select the Options menu > Privacy & Security, scroll down to Security, then select Block dangerous and deceptive content to disable it.