People often install a firewall when what they really wanted was to see what their Mac is doing. Then they spend a week clicking “Allow” on pop-ups for processes they’ve never heard of, and either give up or end up allowing everything. We think that’s backwards.
Two different jobs
A firewall enforces rules. Every connection is checked: allowed, blocked, or put to you as a question. Its output is a decision.
A network monitor observes. It shows which apps connect, to which servers, how much they send and where those servers are. Its output is understanding.
You can’t write good rules without understanding, and understanding doesn’t require rules.
When a firewall is the right tool
- You know an app shouldn’t go online (an offline editor, a game that phones home, an app you’re testing).
- You need to enforce policy on a Mac you manage.
- You want block lists for ads, trackers or malware at the connection level.
On a Mac, turn on the built-in firewall for incoming connections, and add LuLu, Little Snitch or Radio Silence for outgoing ones. Our roundup of Mac firewalls compares them.
When a monitor is the right tool
- You want to know why the network is busy, or which app is uploading.
- You’re curious, or suspicious, about what a new app does.
- You’re troubleshooting: is it the app, the DNS, the server, or the route?
- You want to explain to someone else what their Mac is connecting to, without breaking anything.
Why the order matters
Firewall prompts ask you to make decisions with almost no context: a process name and a host name. A monitor gives you the context: this helper belongs to that app, it connects to its own update server once a day and sends a few kilobytes. After a few days of watching, you’ll know which two or three things are worth blocking, and your firewall rules will be short and correct.
So: monitor first, then block what deserves it. Many people find they never need the second step.
Can you use both?
Yes. A monitor and a firewall don’t compete; LightAtom, for example, doesn’t block anything, so it works alongside any firewall. What you shouldn’t do is run two outbound firewalls at once.
Frequently asked questions
What is the difference between a network monitor and a firewall?
A firewall decides which connections are allowed. A network monitor shows which connections actually happen, with apps, destinations and data volumes.
Do I need a firewall on my Mac?
Turn on the built-in macOS firewall for incoming connections. An outbound firewall such as LuLu or Little Snitch is optional, for when you want to block specific apps.
Can I use a network monitor and a firewall together?
Yes. They do different jobs. Just don't run two outbound firewalls at the same time.
Is Little Snitch a network monitor or a firewall?
Both: it's an outbound firewall with a built-in network monitor.