In the early days of the web, security wasn’t a primary concern. Though, as more information shuttles about the internet, there’s a necessary need for personal and computer security. Though, the protocols we have in place to help will sometimes falter. This could produce the ERR_SSL_PROTOCOL_ERROR in your browser.
To read between the lines, one endpoint can’t verify that a connection is secure when it should be. As such, you’ll see the error. This could be an issue with your browser or the web server, although you’ll want to do some detective work to find the cause.
In this post, we’re going to look at the ERR_SSL_PROTOCOL_ERROR, and discover how to fix it. Before this, let’s talk about what causes the error in the first place, and some context on secure connections.
A Primer On Secure Website Connections
For the unaware, much of the internet runs on secure connections. There are protocols in place to ensure that the data running between the client (i.e. your computer) and server (i.e. the web server) is safe from malicious intent.
You’ll often hear about HyperText Transfer Protocol Secure (HTTPS) connections, and this is the typical standard for the web. While Secure Sockets Layers (SSL) is the most common term for the secure protocol within HTTPS, it’s a depreciated technology. Instead, Transport Layer Security (TLS) is the standard, although you’ll often see an interchangeable reference to SSL.
In a general sense, these protocols combine to encrypt data at one end, protect it from malicious intent throughout the pipeline, and ‘unlock’ it at the other end. You’ll know if a site uses HTTPS, because the domain name will state it in an explicit way. What’s more, almost all browsers will display a ‘padlock’ icon as a visual notification:
In order to enable HTTPS (and therefore, a secure connection), you have to have a certificate installed on your site. In the next section, we’ll look at how this impacts access to your site.
What the ERR_SSL_PROTOCOL_ERROR In WordPress Is
While we’re calling this the ERR_SSL_PROTOCOL_ERROR, browsers will use different names. For example, Chromium-based browsers (such as Chrome itself, and Brave) will display the error as given, but Firefox shows a different version of the error:

You’ll also get plenty of information on screen to help you diagnose the issue (unlike other browsers).
In general, the error relates to a server or client-side computer not being able to verify the security of the website using the SSL certificate. Either end of the connection can cause the error, although as an end user, there’s little you can do if the problem
[…]
This article was written by Tom Rankin and originally published on WPKube.