HTTP Port Reachability Check for a Domain
This tool sends an HTTP HEAD request over HTTP or HTTPS from a server to the domain you enter. It does not send raw TCP probes, accept IP addresses, or identify the software running on a port. The result has four possible states: open means an HTTP response arrived on a port intended for HTTP; closed means the connection was refused; filtered means another connection error or timeout occurred; unverifiable means a response arrived on a port not intended for HTTP. These outcomes describe this probe only and do not confirm a firewall rule or service. Names such as SSH, FTP, and HTTPS are typical labels associated with port numbers, not detected services. Only test domains you are authorised to check, and confirm important findings with tools suited to the protocol and vantage point.
How to check port reachability
- Enter a domain that you are authorised to test. IP addresses are not accepted.
- Leave custom ports empty for the 17 common ports, or enter up to 5 port numbers.
- Choose Check ports. The server sends an HTTP HEAD request per port over HTTP or HTTPS and reports open, closed, filtered, or unverifiable.
- Treat the result as a limited remote HTTP check; verify important findings with a protocol-specific check from the right network location.
When this check can help
- Checking whether a domain responds to an HTTP request on common web ports.
- Comparing a remote HTTP check with an authorised check from inside your network.
- Spotting ports that may need a closer, protocol-specific review.
Frequently asked questions
What does this port check send?
It sends an HTTP HEAD request over HTTP or HTTPS from a remote server. It is not a raw TCP scan and does not test UDP.
What do open, closed, filtered, and unverifiable mean?
Open means an HTTP response arrived on a port intended for HTTP. Closed means the connection was refused. Filtered means another connection error or timeout occurred, which does not confirm a firewall. Unverifiable means an HTTP response arrived on a port not intended for HTTP, so the service cannot be identified.
Does the service column identify what is running?
No. Names such as SSH or HTTPS are typical labels for port numbers. This check does not inspect service banners or identify software.
Why can this result differ from a check inside my network?
This request comes from a remote server. Network location, routing, and perimeter rules can change what responds; the result describes only this HTTP probe.
Can I enter an IP address or scan any host?
The form accepts domains, not IP addresses. Only test a domain when you are authorised to do so, and check the rules and policies that apply to your situation.
Example result
View a fictional HTTP port-check result
Illustrative data only. No domain was queried and no network request is made by opening this example.
Scroll the table horizontally to read every column.
| Port | Result | What it means here |
|---|---|---|
| 80 | open | An HTTP response arrived on an HTTP-oriented port. |
| 22 | unverifiable | An HTTP response arrived, but this check cannot verify an SSH service. |
| 443 | closed | The connection was refused. |
| 8443 | filtered | A timeout or another connection error occurred; this does not prove a firewall caused it. |
These fictional outcomes describe one remote HTTP HEAD check per tested port. Port labels are conventional hints, not detected services or a security verdict.
What the four results mean
Open reports that the HTTP request received a response on an HTTP-oriented port. Closed reports a refused connection. Filtered is used for other connection failures, including timeouts; it does not prove that a firewall caused the failure. Unverifiable is used when an HTTP response arrives on a port whose typical protocol is not HTTP, such as port 22 labelled SSH: the response cannot verify an SSH service. Port labels come from conventional port numbers and are hints only. This check does not test UDP, inspect TCP flags, read service banners, or fingerprint software. Results come from a remote server, so they may differ from checks run inside your network.
- HTTP HEAD reachability probe over HTTP or HTTPS
- Domain input; IP addresses are not accepted
- Four outcomes: open, closed, filtered, and unverifiable
- Typical port-name labels; no service detection
- 17 common ports by default, or up to 5 custom ports (1–65535)
- Results from a remote server, which may differ from an internal check
Free. No signup. Browser tools (subnet, JWT, password strength) run locally; lookup tools query public APIs (Cloudflare DoH, RDAP, certificate logs). Full per-tool breakdown at /methodology/.
Sources (2)
- Fielding, R., Nottingham, M., & Reschke, J. (Eds.) (2022). HTTP Semantics. RFC 9110, IETF (§9.3.2 defines HEAD).
- Internet Assigned Numbers Authority (IANA) (live). Service Name and Transport Protocol Port Number Registry. Conventional port assignments, not service detection.
These are the IETF RFCs, NIST publications, and W3C standards the tool implements or queries. Locate them on the IETF Datatracker (datatracker.ietf.org) or the official standards body.
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