browser reachability test
Browser Reachability Test
Try a no-cors HTTP/HTTPS fetch to a host and port from this browser. This cannot tell open vs filtered vs closed; it only reports whether the fetch succeeds.
Network tool FAQ
Can this tell me if a TCP port is open, filtered, or closed?
No. A browser cannot make raw TCP connections or distinguish those states. The tool only reports whether a no-cors HTTP or HTTPS fetch to the URL succeeds.
Can a browser scan any TCP port?
No. Browser security limits requests to web-style HTTP and HTTPS fetches, so this is not a TCP scanner. Use a server-side or local CLI scanner for that.
Why does a known-open port show as blocked?
CORS, mixed-content rules, TLS errors, firewalls, or non-HTTP services on that port can all stop the browser from confirming reachability.
Which ports work best?
HTTP and HTTPS ports such as 80, 443, 8080, and 8443 are the most suitable for browser reachability checks because the protocol matches what the browser can speak.
Does this test inbound access to my router?
Only if the host and port are publicly reachable by an HTTP or HTTPS fetch from your current network. Non-HTTP services on a router will not produce a useful result here.
What does timeout mean?
The browser did not receive any response before the abort deadline. That is consistent with a closed port, a firewall, a slow host, or simply no HTTP listener at that port.