Open Port Checker
Check whether specific ports are reachable on a host from outside your network. Up to ten ports per check, with the usual service named.
This check runs from our server, not from your browser, and is rate limited. Nothing you enter is stored. Private and internal addresses are refused on purpose.
What this tool is for
Checks whether a port accepts connections from outside, which is the question behind most firewall debugging: the service is running, but is it reachable. Up to ten ports at a time, no ranges. That limit is deliberate, since a tool that scans ranges is a tool for scanning other people networks. This is one of the few tools here that needs a server, because the question is about the internet rather than about your data. The request is made from our server, rate limited, and nothing you enter is stored.
How to use it
- Enter the host you are responsible for.
- List the ports to check, separated by commas.
- Read which answered, which refused and which timed out: the difference matters.
Frequently asked questions
What is the difference between refused and timed out?
Refused means the host answered and nothing is listening: the port is closed but reachable. Timed out means no answer at all, which usually means a firewall dropped the packet silently.
Why can I only check ten ports?
Because port scanning other people infrastructure is what this kind of tool gets used for. Ten ports covers legitimate debugging and is useless for a sweep.
Which ports should not be open to the world?
Databases above all: 3306, 5432, 27017, 6379. Also 22 unless you have hardened it, and any admin panel. If you find these open on your server, that is today problem.