Port Number Lookup is designed for the exact search intent behind “port number lookup”. Look up a port number or service label and review the protocol/service information available in the tool's maintained dataset. Look up a port number or service label and review the protocol/service information available in the tool's maintained dataset. Port numbers and transport protocols TCP and UDP each use 16-bit port numbers from 0 through 65535. The same numeric port can have different context depending on protocol. Registered service names are references Port registries document assigned or commonly associated service names, but applications can run on nonstandard ports and a port number alone does not identify live software with certainty. Lookup is not a port scan This tool should be described as a reference lookup unless it actually connects to a host. It does not prove whether a remote port is open. Worked example: TCP port 443 is commonly associated with HTTPS, but seeing the number 443 in configuration is not by itself proof of a particular server implementation. Common practical uses include Check firewall rules; Review server configuration; Read network logs; Learn common service ports. Important limitations: Registry data can change and should be maintained. A service name does not prove a process is listening. TCP and UDP assignments must not be conflated. Key questions this page should answer include: What range can a port number use? 0 through 65535. Is port 443 always HTTPS? It is commonly associated with HTTPS, but applications can use ports differently. Are TCP and UDP ports the same thing? They share the numeric range but are separate transport-protocol namespaces. Does a port lookup tell me whether a port is open? No. A reference lookup is not a network scan. Where do official service-name assignments come from? The IANA Service Name and Transport Protocol Port Number Registry is the primary standards reference. The page should stay focused on this differentiator: Position the page as a reference lookup, distinguish TCP from UDP and avoid implying that a registered port proves what is actually running on a host.
How to use this tool
Port numbers and transport protocols
TCP and UDP each use 16-bit port numbers from 0 through 65535. The same numeric port can have different context depending on protocol.
Registered service names are references
Port registries document assigned or commonly associated service names, but applications can run on nonstandard ports and a port number alone does not identify live software with certainty.
Lookup is not a port scan
This tool should be described as a reference lookup unless it actually connects to a host. It does not prove whether a remote port is open.
Examples
HTTPS reference example
TCP port 443 is commonly associated with HTTPS, but seeing the number 443 in configuration is not by itself proof of a particular server implementation.
Common use cases
- Check firewall rules
- Review server configuration
- Read network logs
- Learn common service ports
Frequently asked questions
What range can a port number use?
0 through 65535.
Is port 443 always HTTPS?
It is commonly associated with HTTPS, but applications can use ports differently.
Are TCP and UDP ports the same thing?
They share the numeric range but are separate transport-protocol namespaces.
Does a port lookup tell me whether a port is open?
No. A reference lookup is not a network scan.
Where do official service-name assignments come from?
The IANA Service Name and Transport Protocol Port Number Registry is the primary standards reference.