What is port 443 used for?

HTTPS — web traffic encrypted with TLS. It is the default for every https:// URL, and because it is almost never blocked, many other protocols (VPNs, DNS over HTTPS, WebSockets) deliberately ride on it too.

What is the difference between TCP and UDP ports?

They are separate 65,536-slot namespaces. TCP gives ordered, acknowledged delivery — web, mail, databases — while UDP sends without ceremony, suiting DNS lookups, video calls and games. Port 53 TCP and port 53 UDP can be different services, though DNS uses both.

What are well-known, registered and dynamic ports?

0–1023 are well-known, historically requiring administrator rights to bind; 1024–49151 are registered to applications like PostgreSQL's 5432; 49152–65535 are dynamic, handed out by the OS as the source ports of outgoing connections.

Which ports does email use?

Five, for different jobs: 25 for server-to-server SMTP, 587 for authenticated submission from your mail app, 465 for submission over implicit TLS, 143 for IMAP and 993 for IMAP over TLS. POP3's 110 and 995 still linger on older setups.

How do I see which ports are open on my machine?

List listening sockets locally — netstat or ss on Linux, lsof -i on macOS, netstat -ab on Windows — and you get the PID behind each port. This lookup then tells you whether the number matches its conventional service.

Port Number Lookup

Find what runs on any TCP or UDP port, or which port a service uses — searchable both ways, with well-known, registered and dynamic ranges explained.

The Port Number Lookup runs entirely in your browser against a built-in table. No network scanning happens and your searches are never uploaded.

Open the CIDR Calculator

About Port Number Lookup

Port Number Lookup answers both directions of the everyday networking question. Type a number — 5432, 6379, 27017 — and see the service conventionally behind it, its protocol and a one-line description. Type a name — ssh, postgres, https — and find its port. The table covers the ports that actually appear in firewall rules, docker-compose files and error messages: the classic well-known services, mail's tangle of five ports, every major database, and the development staples like 3000, 8080 and 5173. A range banner classifies any number into well-known (0–1023), registered (1024–49151) or dynamic (49152–65535), which explains why your OS picks high random ports for outgoing connections.

Features

Search by port number or by service name
Protocol shown for each entry — TCP, UDP or both
One-line description of what the service actually is
Range classification: well-known, registered, dynamic
Covers databases, mail, web, VPN, gaming and dev-server ports
Exact numeric matches ranked before partial ones
Instant filtering as you type
Everything looked up locally from a built-in table

How to use the Port Number Lookup

Type a port number like 443 or a name like postgres
Read the service, protocol and description from the table
Check the banner for the port's range classification
Clear the search to browse the most common ports

Example

Input

Output

PostgreSQL · TCP · registered range

The default port in every PostgreSQL connection string.

Common errors & troubleshooting

A service runs on a port the table attributes to something else. — Port assignments are conventions, not enforcement — anything can listen anywhere. The table tells you the expected occupant; a process listing on the machine tells you the actual one.
A port is missing from the results. — The table focuses on ports people actually encounter rather than all 65,536. An absent port may still be IANA-registered to something obscure or used privately by one vendor.
Port 8080 turned up several different answers online. — 8080 is the classic HTTP alternate and half the world's dev servers, proxies and dashboards default to it. Context decides — on a CI box it is probably Jenkins, in a compose file probably your own app.
Blocking a port number did not stop the traffic. — Modern services can run over other ports — DNS over HTTPS rides 443, for instance. Firewall by application or destination as well as port when it matters.

Frequently asked questions

What is port 443 used for?: HTTPS — web traffic encrypted with TLS. It is the default for every https:// URL, and because it is almost never blocked, many other protocols (VPNs, DNS over HTTPS, WebSockets) deliberately ride on it too.
What is the difference between TCP and UDP ports?: They are separate 65,536-slot namespaces. TCP gives ordered, acknowledged delivery — web, mail, databases — while UDP sends without ceremony, suiting DNS lookups, video calls and games. Port 53 TCP and port 53 UDP can be different services, though DNS uses both.
What are well-known, registered and dynamic ports?: 0–1023 are well-known, historically requiring administrator rights to bind; 1024–49151 are registered to applications like PostgreSQL's 5432; 49152–65535 are dynamic, handed out by the OS as the source ports of outgoing connections.
Which ports does email use?: Five, for different jobs: 25 for server-to-server SMTP, 587 for authenticated submission from your mail app, 465 for submission over implicit TLS, 143 for IMAP and 993 for IMAP over TLS. POP3's 110 and 995 still linger on older setups.
How do I see which ports are open on my machine?: List listening sockets locally — netstat or ss on Linux, lsof -i on macOS, netstat -ab on Windows — and you get the PID behind each port. This lookup then tells you whether the number matches its conventional service.

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