What is the difference between well-known and registered ports?

Well-known ports run from 0 to 1023 and are assigned by IANA to core services like HTTP (80) and SSH (22); binding them usually needs elevated privileges. Registered ports run from 1024 to 49151 and are assigned to specific applications. Above that, 49152 to 65535 are dynamic or ephemeral ports used for outbound connections.

Can the same port number be both TCP and UDP?

Yes. A port number is meaningful only together with its transport protocol, so TCP 53 and UDP 53 are separate endpoints. DNS uses UDP 53 for normal queries and TCP 53 for zone transfers and large responses, so both are listed.

Why does my service use a non-standard port?

Standard ports are conventions, not rules. Admins move services to non-default ports to avoid conflicts, reduce automated scanning noise, or run multiple instances. Always confirm the actual listening port with a tool like ss or netstat rather than assuming the default.

Which ports should a firewall usually allow inbound?

For a typical web server, 80 (HTTP) and 443 (HTTPS) inbound, plus 22 (SSH) restricted to trusted addresses. Everything else should be denied by default and opened only for services you intentionally expose.

What are ephemeral ports?

Ephemeral ports are short-lived source ports the operating system picks for outbound connections, typically in the 49152 to 65535 range. They are not service assignments, so they do not appear in this reference, but you will see them as the local port of client connections.

Common Port-to-Service Lookup

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Find what’s listening on a port

Network services live on numbered ports. HTTPS is 443, SSH is 22, PostgreSQL is 5432. When you see an open port in a scan, a firewall rule, or a netstat listing, you need to know what it is — and the reverse, the canonical port for a given service. This searchable reference covers the most common TCP and UDP assignments with the service name, transport and the typical daemon or process behind it.

How it works

Each entry pairs a port number with a transport protocol (TCP or UDP), because a port is only meaningful together with its transport — TCP 53 and UDP 53 are different endpoints. The table is filtered live: type a number to find the service, or type a service name to find its conventional port. The transport filter lets you restrict results when you are reasoning about a stateful TCP listener versus a connectionless UDP one. Port ranges follow IANA: 0–1023 well-known, 1024–49151 registered, 49152–65535 dynamic/ephemeral.

Tips and notes

Treat these as conventions, not guarantees — always confirm the real listening port with ss -tulpn or netstat -tulpn rather than assuming the default. Remember that some services need both transports (DNS, NTP) and some use one port for plaintext and another for TLS (HTTP 80 vs HTTPS 443, SMTP 25 vs submission 587 vs SMTPS 465). For firewalls, deny by default and open only the ports you intentionally serve, restricting management ports like SSH to trusted source addresses.