How to add a URL blocklist to the Firefox browser on IGEL OS?

Hello, I am looking for a way to add a URL blocklist to the Firefox browser. I’ve seen some posts on accomplishing this through modifying a json file at browser startup but am lost in the process. Does anyone have any clarification on setting this up?

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Best practice is for your company security / network team to setup a proxy for web traffic so that they can audit / track URLs.

Then all you have to do is enable web proxy in Browser (Firefox or Chromium).

Another option is to setup a non-existent proxy and then provide the list of URLs that are allowed.

No proxy for: List of URLs for which no proxy is to be used

Hi Ron, I am currently using an allow/block list for chromium. We have not tinkered much with Firefox. Do you have a UMS path that this can be accomplished with?

I do not.

If you are blocking a domain, just add a host file to send it to nothing

i.e. ->

That blocks it everywhere

@member there are possibilities in the Firefox browser to block specific URLs or also to let users only access specific URLs, similar like in the Chromium browser. Personally I prefer the Chromium browser, because the configuration options are better described there and easy to configure. Unfortunately I don ́t found a easy and fast solution to configure the specific Firefox preference in the IGEL profile, because the options to configure custom browser policies/preferences with IGEL profiles have a lot of room for improvement.

Here’s my idea:

You have to configure the following custom preference, which can be done in the policy.json file from the Firefox browser. (The policy file is saved in IGEL OS under: /services/fbrw/firefox/distribution/policies.json)

Policy name: “WebsiteFilter”

Policy value: {“Block”:[“:“,”:“]}

…in the policy.json file it could configure with the following line:


( replaced with your URLs to be blocked)

Unfortunately with the Firefox Browser Global -> Advanced options I couldn’t get it resolved quickly. Maybe somebody can help you to add the line described above with a custom command.

(More infos here:

Sorry, I can’t do more in my vacation at the moment. 😕

Why not use a hosts file to send traffic to to a bogus IP, like localhost?

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