Firefox users have plenty of options when it comes to controlling what websites may load when the browser connects to them. Some of the options can be configured right within the browser natively while others come in form of add-ons.
There is the the popular NoScript add-on for example which blocks all scripts by default from being loaded by the browser. Other extensions, such as RequestPolicy can be used to control which cross-site requests are allowed.
Policeman is a new add-on for Firefox that is very similar to RequestPolicy. It allows you to create temporary or permanent rules that determine which contents are allowed to be loaded on or from select domain names.
The core difference to RequestPolicy is that it enables you to do so based on content types. If you don't want images or frames loaded on a domain name for instance, you can create a rule to prevent that from happening.
The add-on ships with a set of native rules to get you started which you can control in the preferences. A click on manage rule sets displays the list of installed sets (the rules that the extension ships with natively) and their priority.
The temporary and persistent rules that you create take priority over same site requests that a domain makes for example. It is possible to change the order of priority or add additional rules to it.
It is for instance possible to add an "allow all" rule after custom rules have been applied to only block requests by sites that you have added specifically to the extension.
Custom rules are created in the preferences as well. An option to do so on the frontend directly, similar to how NoScript handles it, would be much appreciated as it would improve the usability of the process significantly. Rules can be created in the frontend, but only on domains that already have a matching persistent or temporary rule.
You can create temporary or persistent rules, and can make temporary rules at any time persistent. The difference is that temporary rules are only valid for the session while persistent ones across sessions.
If you have created temporary rules you may want to make them persistent before you close the browser as they will be removed automatically from it if you don't.
You can create the following rules:
A basic rule could block scripts from running on a site (which would block most ads for example), or block images from being loaded on it. You can fill out the origin and destination domain or only one of the fields.
Rules are applied on load based on priority rules. To block all images from being loaded on the huffingtonpost.com website, you would simply select Reject images huffingtonpost.com and select add rule.
A click on the extension icon on a site with rules displays information about all rules that are applied.
Policeman is a promising add-on for the Firefox web browser. It could do with usability improvements and instructions on how to use it (this seems planned) though. While not complicated to use, inexperienced users may have a hard time figuring out how to create proper rules using it. All in all though it is a fantastic add-on for the web browser that will certainly be improved by its author over time.
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