Port Numbers List: Common Ports Cheat Sheet

A port number is a 16-bit label that lets one machine run many network services at once. An IP address gets a packet to the right host; the port gets it to the right program on that host. There are 65,536 of them (0 through 65535), and the numbers below are the small handful that people memorize, mistype, or search for over and over.

The three port ranges

IANA splits the space into three bands, and knowing which band a number lives in tells you a lot about it.

Well-known ports, 0 to 1023. Assigned to core services (HTTP, SSH, DNS). On Unix-like systems, binding one usually requires root or an explicit capability.
Registered ports, 1024 to 49151. Assigned by IANA to specific applications on request (databases, app servers). No special privilege needed to bind them.
Dynamic or ephemeral ports, 49152 to 65535. Never assigned permanently. The operating system hands these out as the source port for outbound connections.

Ports also come in two flavours: TCP, which is connection-oriented and ordered, and UDP, which is fire-and-forget. Most services pick one, a few use both, and the tables below note the protocol wherever it is not obvious.

Web

	Port	Protocol	Service
80	TCP	HTTP	Unencrypted web traffic
443	TCP	HTTPS	TLS-encrypted web traffic
8080	TCP	HTTP alt	Proxies, app servers, dev HTTP
8443	TCP	HTTPS alt	Secondary or admin HTTPS

Mail

Mail is the group people get wrong most, because sending and receiving each have an old plaintext port and a newer encrypted one.

	Port	Protocol	Service
25	TCP	SMTP	Server-to-server mail relay
587	TCP	SMTP submission	Sending mail from a client (STARTTLS)
465	TCP	SMTPS	Sending mail over implicit TLS
110	TCP	POP3	Downloading mail, plaintext
995	TCP	POP3S	Downloading mail over TLS
143	TCP	IMAP	Reading mail on the server, plaintext
993	TCP	IMAPS	Reading mail on the server over TLS

For sending mail from an app or client, use 587 with STARTTLS as the default, or 465 for implicit TLS. Port 25 is for server-to-server relay and is blocked outbound by most consumer ISPs and cloud providers to cut down on spam, so it is rarely the right choice from an application.

File transfer and remote shell

	Port	Protocol	Service
20 / 21	TCP	FTP	Data (20) and control (21) channels
22	TCP	SSH / SFTP / SCP	Encrypted shell and file transfer
23	TCP	Telnet	Legacy remote shell, unencrypted
69	UDP	TFTP	Trivial FTP, PXE and network boot
445	TCP	SMB	Windows file and printer sharing
3389	TCP	RDP	Windows Remote Desktop

SSH on 22 is the workhorse here, and the same port carries SFTP and SCP. If you are generating the keys that log in over it, our comparison of Ed25519 vs RSA covers which key type to pick.

Databases

	Port	Protocol	Service
1433	TCP	Microsoft SQL Server	Default MSSQL instance
3306	TCP	MySQL / MariaDB	Default MySQL server
5432	TCP	PostgreSQL	Default Postgres server
6379	TCP	Redis	Key-value store
27017	TCP	MongoDB	Default mongod instance
1521	TCP	Oracle	Default Oracle listener

Infrastructure and directory

	Port	Protocol	Service
53	TCP + UDP	DNS	Name resolution (UDP for queries, TCP for large or zone transfers)
67 / 68	UDP	DHCP	Server (67) and client (68)
123	UDP	NTP	Network time synchronization
161 / 162	UDP	SNMP	Polling (161) and traps (162)
389	TCP	LDAP	Directory queries, plaintext or STARTTLS
636	TCP	LDAPS	Directory queries over TLS
5060	TCP + UDP	SIP	VoIP call signaling

DNS on 53 is the classic “uses both” case. Ordinary lookups go over UDP because they are small and a lost packet is cheap to retry, but responses larger than the UDP limit and full zone transfers fall back to TCP. NTP on 123 and SNMP on 161 stay on UDP, where the low overhead matters more than guaranteed delivery.

Local development conventions

These are not IANA assignments, just habits that frameworks settled on. They are worth listing because they are the ports a developer types most in a day.

	Port	Protocol	Convention
3000	TCP	Node dev server	Next.js, Create React App, Express default
5173	TCP	Vite dev server	Vite's default port
8000	TCP	Python dev server	Django runserver, http.server, Uvicorn

None of the dev ports are reserved, so nothing stops two projects from both wanting 3000. When a tool reports that a port is already in use, another process is simply holding that socket; the number itself carries no special status. Stop the other process or pass a different port.

Finding what is using a port

When a service will not start because its port is taken, you need to find the process holding it. The command differs by operating system, but the idea is the same: list open sockets and match the port.

Check who holds a port

# macOS and Linux
lsof -i :3000

# Linux (modern)
ss -ltnp | grep :3000

# Windows
netstat -ano | findstr :3000

Each of these prints the process ID (PID) bound to the port. Once you have the PID you can stop that process, or start your own service on a different port. On Windows the PID from netstat maps to a process in Task Manager; on macOS and Linux you can pass it to kill. That is far quicker than restarting the whole machine to free the port.

Where to go from here

Ports sit one layer above IP addressing, so this pairs naturally with the subnet cheat sheet when you are reasoning about what can reach what. For the encrypted services in these tables, the plain-English background on what AES encryption is explains what the TLS ports are actually protecting. And when the thing you are looking up is a text pattern instead of a number, the regex cheat sheet is the sibling reference in this set of cheat sheets.

Port numbers list