Point &amp; click to forbid/allow any class of requests made by your browser. Use it to block scripts, iframes, ads, facebook, etc.
uMatrix: A point-and-click matrix-based firewall, with many privacy-enhancing tools.

uMatrix put you in full control of where your browser is allowed to connect, what type of data it is allowed to download, and what it is allowed to execute. Nobody else decides for you: You choose. You are in full control of your privacy.

Out of the box, uMatrix works in relax block-all/allow-exceptionally mode, meaning web sites which require 3rd-party scripts are likely to be &quot;broken&quot;. With two clicks, uMatrix can be set to work in allow-all/block-exceptionally mode, which generally will not break web sites.

Regarding the myth that &quot;Chromium-based browsers can&#39;t reliably block JavaScript&quot;, see: https://github.com/gorhill/httpswitchboard/wiki/Blocking-javascript-execution-reliably-in-Chromium-based-browsers.

* See ALL the remote connections, failed or attempted, depending on whether they were blocked or allowed (you decide).

* A single-click to whitelist/blacklist one or multiple classes of requests according to the destination and type of data (a blocked request will NEVER leave your browser).

* Efficient blacklisting: cookies won&#39;t leave your browser, JavaScript won&#39;t execute, plugins won&#39;t play, tracking pixels won&#39;t download, etc.

* You do not have to solely rely on just one particular curated blacklist (arguably with many missing entries) outside which nothing else can be blocked: You are in full control.

* Ease of use: uMatrix lets you easily whitelist/blacklist net requests which originate from within a web page according to a point-and-click matrix:

- domain names (left column)
* from very specific
* to very generic

- type of requests (top row)
* cookies
* CSS-related resources (stylesheets and web fonts)
* images
* plugins
* scripts
* XHR (requests made by scripts)
* frames
* others

uMatrix

Windows

Linux

Google Chrome

Opera

Chromium

Firefox

Point &amp; click to forbid/allow any class of requests made by your browser. Use it to block scripts, iframes, ads, facebook, etc.

When a program attempt to connect to the Internet.

Simple tool to configure Windows Filtering Platform (WFP) which can configure network activity on your computer.

The lightweight application is less than a megabyte, and it is compatible with Windows Vista and higher operating systems. You can download either the installer or portable version. For correct working, need administrator rights.

Features:
   - Simple interface without annoying pop ups.
   - Rules editor (create your own rules).
   - Internal blocklist rules (block Windows spy / telemetry).
   - Dropped packets information with notification and logging to a file feature (win7+).
   - Allowed packets information with logging to a file feature (win8+).
   - Windows Subsystem for Linux (WSL) support (win10).
   - Windows Store support (win8+).
   - Windows services support.
   - Free and open source.
   - Localization support.
   - IPv6 support.

simplewall

Simple tool to configure Windows Filtering Platform (WFP) which can configure network activity on your computer.

LuLu is the free, shared-source firewall for macOS. Its goal is simple; block any unknown outgoing connections, until approved by the user. While it was designed to generically detect malware by flagging unauthorized networking connections, LuLu can also be used to block OS components or 3rd-party applications from transmitting information to remote servers. 

What&#39;s to like about LuLu? Lots!  

100% free
As in no ads, no time trials, no missing features. Because why not!? 
And no, it doesn&#39;t track, monitor, or spy on you - as that&#39;d just be pure evil!


Shared source
The full source code for LuLu is available on GitHub. Such transparency allows anybody to audit its code, or understand exactly what is going on.


Protects
LuLu aims to alert you whenever an unauthorized network connection is attempted. As such, it can generically detect malware, or be used to block legitimate applications that may be transmitting private data to remote servers.


Simple
&quot;Do one thing, do it well!&quot; LuLu is designed as simply as possible. Sure this means complex features may not be available, but it also means it&#39;s easier to use and has a smaller attack surface!


Enterprise-friendly
Want to know what network events are being detected? Or rules your users have added? LuLu provides simple mechanisms to subscribe to such events, and stores data such as rules in an open, easily digestible manner.


LuLu by Objective-See

LuLu is the free, shared-source macOS firewall that aims to block unknown outgoing connections unless explicitly approved by the user.

In Windows, you can use Windows Firewall to block or unblock certain applications, but it doesn’t offer an easy-to-use interface for its advanced features. Firewall App Blocker makes the process very easy! Simply drag and drop the application you wish to block into the FAB window, or browse the hard disk to find it and block it through context menu. That’s it! If you want to allow it access again, you need only select it and press the Delete button.

FAB doesn’t do anything that Windows can’t do itself, however it provides a much simpler means to select which programs will be blocked. Best of all, it makes it very easy to add multiple programs to the firewall simultaneously!

Firewall App Blocker

Friendly user interface for blocking selected applications through built in Windows Firewall.

IceFloor is the first OS X free graphic frontend for PF. Configure the PF firewall in a few clicks using a very simple interface and a step by step in-app configuration guide (Quick Start). 

Apps with 'Outbound firewall' feature

uMatrix

simplewall

LuLu by Objective-See

Firewall App Blocker

IceFloor