Turning on the macOS firewall blocks unwanted incoming connections to your Mac from other computers. It does not cut off every incoming connection or disable every network service. Apps and sharing services that are permitted still work, and the setting does nothing to your outgoing traffic. Knowing that boundary keeps you from assuming a Mac with the firewall on is unreachable when it is simply filtering.
What the firewall controls
Apple describes the built-in firewall as protection against unwanted network access and denial-of-service attacks. In Apple’s words, “A firewall can protect your Mac from unwanted contact initiated by other computers when you’re connected to the internet or a network.” (Apple Support, “Block connections to your Mac with a firewall”)
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That is the whole job of the setting: it decides which incoming connection requests reach your Mac’s apps and services. It is not encryption, it is not malware scanning, and Apple’s firewall pages make no claim that it replaces router security. Those are separate protections, and a reader who wants them needs different tools.
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The firewall also does not treat every service the same. Apple notes that sharing services can open specific ports, and that apps or services can be allowed through the firewall. So the practical result of turning it on is a filtered Mac, not a closed one.
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How to turn it on
Apple’s current Mac Help places the setting here:
- Click the Apple menu, then choose System Settings.
- Click Network in the sidebar. On some windows you may need to scroll down to find Firewall.
- Click Firewall, then switch Firewall on.
Menu labels change between macOS releases. Apple’s February 18, 2021 security overview, “Firewall security in macOS”, describes an older path, System Settings > Privacy & Security on macOS 13 and later, and Security & Privacy in System Preferences on macOS 12 or earlier. If your menu does not match the steps above, check which macOS version you are running before following a different guide.
The Firewall settings, one by one
Once the firewall is on, the Options button opens the per-app controls and the additional switches. Apple says Options is greyed out until the firewall is turned on.
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Options: allow or block a specific app
The Options list shows apps and services that have been given a rule. You can add an app or service if it is missing, then choose whether it may receive incoming connections. Apple warns that blocking an app’s access can interfere with that app or with other software that depends on it. Test the app after any change you make here.
Apps that do not appear in the visible list can still have access. Apple names system processes and certain digitally signed apps that other apps launch automatically as examples. This means the list is not a complete inventory of what can reach your Mac.
Block all incoming connections
This switch blocks incoming connections to non-essential services and apps. Apple says basic internet services remain available, so ordinary web browsing and similar outbound activity keep working. It also blocks connections to other sharing services, but Apple notes that a sharing service enabled in Sharing settings may still connect through the firewall. To restrict further, turn off any sharing service you do not use in System Settings > General > Sharing. (Apple Support, “Change Firewall settings on Mac”)
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Automatically allow built-in software
When this is on, qualifying built-in apps and services signed with a valid certificate may be added to the allowed list without asking you. Use it when you want Apple’s own software to work without prompts while everything else is filtered.
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Automatically allow downloaded signed software
This option works the same way for downloaded apps and services that carry a valid signature. Unsigned software does not qualify, so it will still trigger a prompt or be blocked.
Stealth mode
With stealth mode on, the Mac does not answer unauthorized probing requests, including ICMP ping. Apple notes that it still responds to requests from authorized apps. Stealth mode makes the Mac less responsive to scans. It does not make the Mac invisible, and it does not block all network traffic.
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Allow prompts for new apps
When an app not yet on the list tries to accept an incoming connection, macOS can show an alert asking whether to allow or deny it. Until you respond, the attempt is denied. Choose Allow only for software you recognize and expect to receive connections.
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| Your goal | Settings to use | What to check afterward |
|---|---|---|
| Block most unsolicited incoming access on a laptop used in cafés or airports | Firewall on; Block all incoming connections on; Stealth mode on | Confirm that file sharing, screen sharing and any other service you rely on are turned off or still working |
| Keep a Mac that shares files or screens with others on your network | Firewall on; leave Block all incoming connections off; allow the specific sharing app in Options | Test the share from another device, because blocking the app can stop it |
| Let Apple software work without prompts | Automatically allow built-in software on | Expect fewer prompts for built-in apps, not for unsigned downloads |
| Reduce the Mac’s response to scans | Stealth mode on | Authorized apps still respond, so test them after enabling |
When something stops working
If an app or sharing feature fails after you turn the firewall on, work through these checks in order:
- Open System Settings > Network > Firewall > Options and find the app. If it is listed as blocked, change it to allowed.
- If the app is missing from the list, add it using the controls in Options, then choose allow.
- Turn off Block all incoming connections and test again. If the feature works, the blanket block was the cause.
- Open System Settings > General > Sharing and confirm the service you want is enabled, since Apple’s guidance is to disable unused sharing services rather than rely on the firewall alone.
- Restart the app or the Mac after changing rules, then test from the other device.
Managed Macs
If your Mac belongs to a work or school fleet, an administrator may set the firewall through a device management Firewall payload. Apple’s deployment documentation lists app allow and block rules, stealth mode and logging among the options, notes that some options require particular macOS versions, and says each management service implements the settings differently. The steps in this article are for personal Macs; for managed devices, follow the policy your administrator set. (Apple Support, “Firewall device management payload settings for Apple devices,” published October 24, 2022)
The Bottom Line
Turn the firewall on, then decide how strict you want incoming access to be. For most personal Macs, leaving Block all incoming connections off, keeping stealth mode on, and allowing only the apps you use for sharing gives a reasonable balance. Turn on the full block when you are on an untrusted network and do not need incoming access, and test any sharing feature you rely on afterward.
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