How to use the Port Numbers Reference
- 1. SearchType a port number like 3389 or a service like SSH.
- 2. Filter by categoryPick web, email, databases, DevOps and more.
- 3. DownloadSave the list as text for your notes or a firewall review.
How port numbers work
An IP address finds the machine; a port number finds the service on it. Ports run from 0 to 65535. The Internet Assigned Numbers Authority (IANA) registers well-known ports (0–1023) and registered ports (1024–49151); the rest are dynamic ports used for the client side of connections. TCP is used when every byte must arrive in order, UDP when speed matters more, as with DNS lookups and video calls.
Example: 3389 · RDP is Windows Remote Desktop. It is one of the most attacked ports on the internet, so the advice is to put it behind a VPN and require MFA rather than expose it directly.
Using the list for security
- Close what you do not use. Every open port is a door someone can knock on.
- Never expose databases such as 3306, 5432, 6379, 9200 or 27017 to the internet; many data leaks started there.
- Replace plain-text protocols: Telnet with SSH, FTP with SFTP, HTTP with HTTPS, POP3/IMAP with their TLS versions.
- Remember the defaults are conventions. Services can run on any port, and attackers often use common ones such as 443 to blend in.
Development ports such as 3000, 5000 and 8000 are framework defaults, not IANA assignments. This list covers the ports you meet most often; the full IANA registry has thousands more. Scan only networks you own or are authorised to test. Configure safe web headers with the CSP generator, and set the port your container exposes with the Dockerfile generator.
Frequently asked questions
Is port 443 always HTTPS?
Usually, but any service can listen on any port. HTTP/3 also uses UDP 443.
Why are there two numbers for some services?
Some protocols use one port for control and another for data, or one for plain and one for TLS, such as 1883 and 8883 for MQTT.
Is the Port Numbers Reference free?
Yes, the Port Numbers Reference is free. The first time you download the list, you are asked for your name and WhatsApp number once. After that, this and every other Uncodemy tool opens straight away without the form.