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Check if network ports are open or closed on remote hosts and test network connectivity.
Read this first: browsers cannot do a real port scan.
Web pages cannot open raw TCP sockets, so a true port scan is impossible from the browser. This tool only makes an HTTP(S) request and infers reachability from timing and errors. It can only meaningfully test ports that speak HTTP or HTTPS, and the results are heuristic, not authoritative. For real port scanning use a server-side tool such as nmap.
This port checker performs a best-effort reachability test for a given host and port from within your browser. You enter a host name and a port — or pick a common preset such as 80, 443, or 5432 — and the tool reports whether the port responded, timed out, or refused the connection.
There is an important limitation to understand first: web pages cannot open raw TCP sockets, so a browser cannot perform a true port scan the way a tool like nmap does. Instead, this tool makes an HTTP(S) request to the host and port and infers reachability from the timing and any errors. The request goes out from your browser to the target host over the network. This means it can only meaningfully test ports that speak HTTP or HTTPS, and every result is a heuristic hint rather than an authoritative answer.
A "Responded" result means a web-capable service answered. "Timed out" means nothing replied before the five-second limit — the port could be filtered, closed, or running a non-HTTP service the browser cannot talk to. "Refused / unreachable" means the connection failed quickly, typically a closed port or an unreachable host. For definitive port scanning, use a server-side tool.
No. Browsers cannot open raw TCP sockets, so this tool only makes an HTTP(S) request and infers reachability from timing and errors. For a true port scan, use a server-side tool such as nmap.
The logic runs in your browser, but the check itself sends a network request from your browser to the host you enter, so the target host does receive a connection attempt.
Because it uses an HTTP(S) request, it can only meaningfully evaluate ports that speak HTTP or HTTPS. A database or SSH port may time out even when the service is running and reachable.
It means nothing answered within five seconds. The port could be filtered by a firewall, closed, or simply running a service the browser cannot speak to — the tool cannot tell these apart.
The browser cannot distinguish a genuine TCP handshake from a TLS or CORS rejection, so results are heuristic. Treat every outcome as an indication rather than a definitive answer.