What are well-known ports?

Well-known ports are the range 0 to 1023, assigned by IANA to core internet services such as HTTP, SSH, and DNS. On most operating systems, binding to a port in this range requires administrative privileges.

What is the difference between TCP and UDP for a port?

TCP is connection-oriented and reliable, used by services like HTTP and SSH. UDP is connectionless and lightweight, used by DNS queries, DHCP, and NTP. Some services, like DNS, use both depending on the message size.

What service runs on port 443?

Port 443 is HTTPS, which is HTTP over TLS. Modern browsers also use it for HTTP/3, which runs over UDP using QUIC, so 443 carries both encrypted web traffic over TCP and over UDP.

Why are ports 1024 and above not listed here?

Ports 1024 to 49151 are registered ports assigned to specific applications, and 49152 to 65535 are dynamic or ephemeral ports used for outgoing connections. This reference focuses on the well-known range 0 to 1023.

Should I open all these ports on my firewall?

No. Open only the ports for services you actually run, and prefer the encrypted variants such as 22, 443, 465, 993, and 995. Leaving unencrypted legacy services like Telnet on port 23 exposed is a security risk.

TCP/UDP Well-Known Port Reference

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Look up any well-known port

Network services listen on numbered ports, and the lowest range — 0 to 1023 — is reserved for the core protocols of the internet. IANA assigns these well-known ports so that, for example, web traffic always finds a server on port 80 or 443. This reference lets you search by port number, service name, or keyword and shows the assigned service and transport protocol.

How it works

Every entry follows the IANA Service Name and Transport Protocol Port Number Registry. A port assignment specifies a number, a service name, and whether the service uses TCP, UDP, or both. TCP is reliable and connection-oriented; UDP is fast and connectionless. Some services appear under both — DNS on port 53 uses UDP for small queries and TCP for larger transfers and zone moves. The search matches your query against the port number, the service name, and the description.

Tips and notes

Prefer encrypted services where they exist: SSH (22) instead of Telnet (23), HTTPS (443) instead of HTTP (80), and the TLS mail ports — SMTPS (465), submission with STARTTLS (587), IMAPS (993), and POP3S (995). Binding to a well-known port usually requires root or administrator rights, which is why application servers often run on higher ports behind a reverse proxy. Ports above 1023 fall outside this reference: 1024 to 49151 are registered, and 49152 and up are dynamic. All lookups run locally in your browser.