Firewall Checker

You set a firewall rule. Does it actually do what you wanted? Firewall Checker is a controlled-test program that tries to reach the internet from your machine. If your rule blocks it, the test shows "blocked". If your rule permits it, the test shows "allowed". No guesswork.

What it does

Run Firewall Checker. It opens an outbound connection to a remote test server. Your firewall sees a new program reaching out and either lets it through (matching an allow rule) or stops it (matching a deny rule). The program reports the outcome.

When you need it

• You configured a Windows Defender Firewall rule and want to confirm it works
• You want to verify that a deny-all-except-X policy actually denies
• You set up a third-party firewall and aren't sure its rules took effect
• You need a reliable "permitted program" target to test allow rules

Features

• Tests both block and allow scenarios
• Single portable executable — the test target itself
• Configurable destination and port
• No installer, no registry edits

System requirements

• Windows 7, 8, 10, 11 (older versions still supported)
• An active firewall to test against (Windows Defender, ZoneAlarm, Comodo, etc.)
• About 1 MB of disk space