distribution/policies.json needs to be in the directory where the Firefox binary is. It could be anywhere but is often in /opt/firefox so the full path would be /opt/firefox/distribution/policies.json.

The easiest way to find it is in Firefox press Alt-H and then choose "More Troubleshooting Information" from the drop-down menu that appears. In the first block of information is a line starting with "Application Binary" with the path next to it. That's where to put distribution/policies.json.

distribution/policies.json needs to be in the directory where the Firefox binary is. It could be anywhere but is often in /opt/firefox so the full path would be /opt/firefox/distribution/policies.json. The easiest way to find it is in Firefox press Alt-H and then choose "More Troubleshooting Information" from the drop-down menu that appears. In the first block of information is a line starting with "Application Binary" with the path next to it. That's where to put distribution/policies.json.

Appreciate the clarification.

However, if placed there, the policies apply to all profiles opened using that binary.

Yet I need a more fine grained control, so that I can have different policies for different profiles. E.g. profileA: no restrictions profileB: about config not allowed, no connections other than localhost allowed.

All I've ever done with Policies is stop Thunderbird up-dating so can't really help you further.

I would have thought that there'd be some way of saying in the Policy file which things to apply to which profiles. Also if it worked in the ~/.mozilla/firefox/profile directory a user could edit it whereas in /opt or /usr/bin they'd need root permissions.

policies.json works for all profiles, so you can't have different settings unless you would use multiple installations, each in its own installation folder.

You can however use an autoconfig.cfg file as this file supports JavaScript if you disable the sandbox and in such a case you can place pref settings in an 'if' block that detects the name of the profile.

• https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig

Content of autoconfig.cfg:

// start autoconfig.cfg with a comment line
let Services = globalThis.Services
let profD = Services.dirsvc.get("ProfD", Ci.nsIFile).path;

Content of autoconfig.js:

//start autoconfig.js with a comment line
pref("general.config.filename", "autoconfig.cfg");
pref("general.config.obscure_value", 0);
pref("general.config.sandbox_enabled", false);