How to remove Firefox's "This address is restricted", commonly triggered by trying to access port 87

Here is a quick guide on how to remove Firefox's error message when trying to access resources on restricted ports, such as port 87

Here is a quick guide on how to remove Firefox's error message when trying to access resources on restricted ports, such as port 87:

This address is restricted

This address uses a network port which is normally used for purposes other than Web browsing. Firefox has canceled the request for your protection.

Step 1 - Open Firefox's settings: about:config

Open Firefox's preferences by typing the following URL in Firefox:

about:config

You might get a warning that you are entering sensitive configuration, if so, continue with caution:

Step 2 - Find the settings network.security.ports.banned.override

In the filter box, type in:

network.security.ports.banned.override

Step 3 - It has to be a String of comma separated list of ports

I have noticed that simply toggling this to "false" or deleting it does not actually permit restricted addresses.

Instead what we need is to have this preference as a String of comma separated list of ports.

So if you already have this preference (as a Boolean), simply delete it:

Then recreate the preference as a "String":

Next add "87" as the value and save it:

Afterwards it should look something like this:

If needed, you can also specify multiple ports either as a range such as "1-1024" or even combine with a comma separated list such as "87, 150-300, 350, 400, 450-500".

Step 4 - Refresh the page

Just refresh the page and you should have no problems accessing the resource.