Little Snitch monitors every app's network connections on macOS and lets you allow or block them in real time. See pricing, features, and pros and cons.
Little Snitch, made by Objective Development, is a network monitor and application firewall for macOS. Rather than only blocking incoming traffic like a traditional firewall, it watches outgoing connections too: whenever an app tries to reach the internet, Little Snitch can alert you and let you decide whether to allow or deny it. Silent Mode lets connections through automatically while logging them for later review, and a 12-month traffic history with an interactive, map-based view shows which apps are talking to which servers around the world.
Rules can be scoped by server, domain, port, or protocol, grouped into local or remotely-subscribed rule groups, and applied to whole application groups (including macOS system processes) rather than one app at a time. Little Snitch can also switch between rule profiles automatically based on which Wi-Fi network you're connected to, encrypt DNS lookups (DoH/DoT/DoQ) via Quad9, and apply curated, daily-updated blocklists to cut off trackers and known-bad domains. A command-line utility is included for scripting and advanced control.
The product has been sold by Objective Development, an Austrian software company founded in 2004, for more than 20 years and is aimed at privacy-conscious Mac users and IT/security professionals who want visibility into and control over their machine's outbound network activity.