Best Firewall and Network Monitors for Mac

The short answer. Start with LuLu if you want the core job done for free: it is open source and alerts you to every new outgoing connection with rules you can scope and time-limit. Little Snitch is the one to pay for if you want fine-grained rules, profiles, blocklists and encrypted DNS in one place. Sniffnet is a different kind of tool and worth being clear about: it shows you your traffic, it does not block it — choose it to understand what is happening, not to stop it.

This guide covers 3 firewall and network monitors for macOS. Every fact below is drawn from the same verified records that back each app’s own page. The recommendations are our editorial judgment, not payment. Last verified 2026-10-05.

Quick comparison

What actually decides this

• Blocking versus observing. These get grouped together and they are opposites. A firewall decides whether a connection happens; a network monitor shows you connections that already happened. Picking the wrong one leaves you watching traffic you meant to stop.
• Rule granularity. The useful question is how precisely you can say “this app, to this host, on this port, for the next hour”. A tool that only offers allow-or-deny per application pushes you toward either blanket trust or blanket blocking.
• How noisy it is. An outbound firewall works by asking you questions. If it asks too many, you approve them without reading, and the tool stops protecting you. The quality of the defaults and the ability to time-limit a rule matter as much as the rule engine.
• Cost and licensing. An open-source firewall and a paid one can cover the same core job. What the paid version tends to add is convenience — rule groups, profiles, blocklist subscriptions — rather than the ability to block.
• What it can and cannot see. A local firewall sees which application opened a connection and to where. It cannot see inside an encrypted stream, and it cannot judge whether a permitted connection was a good idea. It is a gate, not a verdict.

Our picks

• LuLu — It is open source and alerts you to every new outgoing connection, with scoped and time-limited rules, allow and block lists, profiles and a bundled network monitor. Choose it when you want outbound blocking for free and will read the alerts.
• Little Snitch — It asks before any app connects out and adds rule groups, profiles, blocklists and encrypted DNS, which is the layer of convenience on top of the same core job. Choose it when you want fine-grained control and are happy to pay once for it.
• Sniffnet — It charts live traffic, names the programs using your bandwidth and identifies the remote hosts and services behind each connection — a monitor, not a firewall. Choose it when you want to understand your traffic rather than block it.

The apps

Little Snitch

Little Snitch is a firewall for macOS. macOS network monitor and personal application firewall that asks before any app connects out, with rule groups, profiles, blocklists and encrypted DNS. It is one-time purchase.

Strengths. According to the developer, shows a connection alert whenever an app wants to connect, so nothing goes out without a decision. Records server location, port, protocol and data volume for each connection. Provides an interactive traffic chart covering up to twelve months of history.

Trade-offs. Costs $59 for a single licence, where some comparable Mac firewalls are free. Closed source, so the filtering implementation cannot be inspected. Version 4 does not support Apple silicon; only version 5 and later run on M-series Macs. Mac-only; there is no Windows or Linux version. The length of the free trial is not stated in the sources Nuanyue tracks.

Not for. Anyone who needs an open-source firewall they can inspect — Little Snitch is closed source. Users who want a free tool, since it is sold as a paid licence. Windows or Linux users, as it is a Mac-only application.

What it does. Connection alerts asking whether an app may connect out. Silent Mode, which allows new connections at first and defers the decision. Real-time view of every connection, with server location, port and protocol. Interactive traffic chart covering up to twelve months of history.

Little Snitch is listed with current version 6.5.

Full profile and verified facts for Little Snitch →

LuLu

LuLu is a firewall for macOS. Free, open-source macOS firewall that alerts you to every new outgoing connection, with scoped and time-limited rules, allow and block lists, profiles and a bundled network monitor. It is released under GPL-3.0.

Strengths. According to the developer, alerts on every new or unauthorized outgoing connection, showing the process and the destination with block and allow actions. Alert details include code-signing information, the process hierarchy and a VirusTotal lookup button. Rules can be scoped to an entire process or to just the remote endpoint, and given a duration of always, the process lifetime, or a set expiry.

Trade-offs. macOS only — there is no build for other platforms. According to the developer, it covers outgoing connections only; Apple’s built-in firewall is what blocks incoming ones. Until rules have accumulated, answering a prompt for each new connection is intrusive. Only rules you created yourself can be exported. Whether the current release is a universal binary is not stated in the sources Nuanyue tracks; Objective-See publishes a single disk image for macOS 10.15 and later.

Not for. Anyone who needs long-term traffic history and per-connection reporting, which a network monitor provides and a firewall does not. People who do not want to answer connection prompts at all.

What it does. Alerts whenever a new or unauthorized outgoing connection is created. Alerts show the process name and destination, with block and allow actions. Alert details include code-signing information, the process hierarchy and a VirusTotal lookup. Rules grouped as All, Default, Apple, 3rd-party program, User and Recent.

LuLu is listed with current version 4.5.1.

Full profile and verified facts for LuLu →

Sniffnet

Sniffnet is a network monitor for macOS. Free open-source network monitor for macOS that charts live traffic, names the programs using your bandwidth, and identifies the remote hosts, services and malware families behind each connection. It is released under MIT OR Apache-2.0.

Strengths. According to the developer, recognises more than 6000 upper-layer services, protocols, trojans and worms, so a connection can be named rather than shown as a bare address. Shows which programs are using network bandwidth, which answers the usual ‘what is eating my connection’ question directly. Resolves the domain name, ASN and geographic location of the hosts you are exchanging traffic with.

Trade-offs. Observes traffic but cannot block it; the IP blacklist highlights a suspicious connection rather than preventing it. Analysing a network adapter on macOS requires running the application with administrator privileges. Summarises traffic rather than dissecting individual packets field by field, so it does not replace a protocol analyser such as Wireshark. It monitors traffic rather than controlling it; it is not a firewall and cannot stop a connection being made. The minimum macOS version for the current release is not stated in the sources Nuanyue tracks.

Not for. Anyone who needs to block or filter traffic — Sniffnet observes connections, it does not control them. Users who need field-by-field dissection of individual packets, which is what a protocol analyser is for.

What it does. Choose which network adapter to inspect. Filters that narrow the traffic being observed. Import and export capture reports as PCAP files. Overall statistics for your internet traffic.

Sniffnet is listed with current version 1.5.1.

Full profile and verified facts for Sniffnet →

How to choose

• No licence fee, source available. LuLu and Sniffnet — the source can be read and, under the terms of each licence, reused.
• One-time purchase. Little Snitch — you pay once.

Open source: LuLu and Sniffnet (2 of 3).

Common mistakes

• Expecting a network monitor to block anything. Sniffnet shows you connections; it does not stop them, and no amount of configuration changes that.
• Approving every prompt without reading it. Alert fatigue is how an outbound firewall quietly becomes an allow-everything list with extra steps.
• Assuming the built-in macOS firewall filters outgoing connections. It is an inbound firewall; blocking apps from calling out is what these tools add.
• Expecting a firewall to inspect encrypted traffic. It can tell you which app connected and to which address, and beyond that it is guessing like anyone else.

How this guide was put together

Each app’s facts come from its own record: the developer’s own pages and repository, the App Store listing where one exists, and the documentation, each with a source grade and an access date. Where a fact rests on the developer’s own statement rather than on something we verified independently, the sentence says so. Where our data has no value for something, the guide says “not published” instead of guessing.

A price appears here only where the record carries one from a stated source; the guide never estimates one, and it records the pricing model alongside so the two can be read together. Prices change and vary by region, so each app links to its own page for the current detail.

The facts and the recommendations are kept apart on purpose. Everything in the app entries, the comparison table and the answers above is composed from the records. The short answer, the criteria and the picks are our editorial judgment: they reflect what we would choose and why, and they are not paid for. Where we make a recommendation we name the condition it applies under, because we do not call anything “the best” without explaining the criteria.

Verified 2026-10-05.