Getting Started

Little Snitch for Linux is operated entirely through a web interface. You can use it in a regular browser tab, but for daily use we recommend installing it as a Progressive Web App (PWA). A PWA gets its own window, its own icon in your application launcher and task bar, and feels closer to a native application.

Installing as a Progressive Web App

With a Chromium based browser (Chrome, Chromium, Edge, Brave, Vivaldi, ...)

Chromium based browsers support PWA installation natively:

Navigate to http://localhost:3031/.
Click the install icon that appears in the address bar. If you do not see it, open the browser menu (the three dots) and choose "Install app" or "Cast, save, and share" and then "Install page as app", depending on the browser version.
Confirm the installation.

Little Snitch now opens in its own window and appears in your application launcher.

Chromium address bar with the PWA install icon highlighted

With Firefox

Firefox does not support installing PWAs out of the box. A browser extension adds this capability:

Install the extension "Progressive Web Apps for Firefox" from addons.mozilla.org.
On first run, the extension opens a setup wizard. Accept the license agreement and let the wizard install its native helper program and a dedicated Firefox runtime. This is a one time step.
Navigate to http://localhost:3031/.
Click the install icon that appears in the address bar and confirm.

Firefox with the PWAs for Firefox install icon in the address bar

Which browser should you choose?

Both approaches work well. The trade offs:

Firefox with the PWA extension

Advantage: The PWA runs as a separate executable in an isolated profile. It has its own icon and its own storage for passwords and cookies, separate from your main browser. Because it is a separate executable, you can create Little Snitch rules that apply to this particular instance only.
Disadvantage: The extension maintains its own Firefox runtime for installed apps. You will receive separate update notifications for it, independent of your main Firefox, and you must handle these updates manually.

Chromium based browsers

Advantage: The PWA is the same executable as your main browser, so there are no separate updates to handle.
Disadvantage: The window uses the browser's icon rather than the Little Snitch icon. Passwords and cookies are shared with your main browser. And because it is the same executable, Little Snitch rules for the PWA are the same rules as for your main browser. You cannot give the PWA stricter rules.

The three main views

The interface is organized into three main sections:

Connections shows current and past network activity, grouped by application. This is where you will spend most of your time. See Watching Your Connections.
Rules lists all rules you have created and lets you edit them. See Writing Your Own Rules.
Blocklists manages subscription based lists that block whole categories of unwanted traffic. See Blocklists.