A future versions of Firefox could introduce a HTTPS-only browsing mode that would technically block insecure websites from loading.

The latest version of Firefox 76, which is currently available as part of the Nightly channel, introduces this new option under an experimental flag, so Mozilla could release it to everyone in the coming months.

So what does this new HTTPS-only browsing mode do?

First and foremost, browser makers have been trying to push the web to HTTPS for a long time already, and while the majority of sites have already been upgraded to this secure protocol, others continue to use HTTP.

Once the HTTPS mode is activated in Mozilla Firefox, HTTP websites would no longer load. The browser will first try to reach the server for an HTTPS version, and in case it doesn’t exist, users are provided with an error message reading “Secure Connection Failed”.

As per Sören Hentzschel, you can already try out the feature by installing the latest Firefox Nightly on your device.

Once you launch the browser, type the following code in the address bar to enter the experimental flag section:

about:config

Next, you can use the search box at the top to find the following flag in Firefox:

dom.security.https_only_mode

By default, the flag is currently configured to false, which means it’s disabled – this makes sense given it’s just an experimental feature for the time being; additionally, it’s very likely to remain an optional feature once it makes its way to the stable version of the browser.

So what you need to do is click the toggle button to switch the flag to the true value, which means it’s then activated. At this point, the HTTPS-only mode is up and running, so HTTP websites would no longer load until you disable the flag by switching back to the false state.