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Port Number Lookup

Find what runs on a port, with a note on whether it should be exposed.

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Quick Tool Overview

The Port Number Lookup maps port numbers to services and back, covering the well-known ports plus the development server ports that actually come up, with notes on which should never face the internet.

What it does
Looks up what runs on a TCP or UDP port
You give it
A port number or a service name
You get back
The service, protocol and an exposure note
Best for
Firewall rules, and finding what is holding a port
Developer Tools Free, unlimited use No sign-up Runs in your browser

About the Port Number Lookup

Search a port number to find what normally listens on it, or search a service name to find its port. The list covers the well-known ports plus the development server ports that actually come up day to day — 3000, 5173, 8080, 9000.

Each entry has a note on what the service is and, where it matters, on exposure. Some ports should never face the internet: 3306, 5432, 6379, 27017, 445 and 3389 are all routinely scanned and routinely compromised, and Redis and Memcached in particular ship with no authentication at all. The ports that are also amplification vectors for denial-of-service traffic are marked, since those cause trouble for other people as well as for you.

Key features of the Port Number Lookup

Exposure warnings

Database ports, Redis, Memcached, SMB and RDP are flagged as ports that are scanned constantly and should stay behind a firewall.

Development ports included

3000, 4200, 5173, 8000 and 8080 are in the list, because those are the ones you actually collide with.

Search both ways

Type 5432 or type postgres — either finds the entry.

The macOS port 5000 trap

AirPlay Receiver binds it, which is the usual reason a Flask or .NET server will not start, and it is noted on the entry.

Protocol shown

TCP, UDP or both, since a number can mean different services on each.

How to use the Port Number Lookup

  1. 1

    Search a number or a name

    Type 5432, or type postgres — either finds the entry.

  2. 2

    Read what uses it

    The service, the protocol and what it is for.

  3. 3

    Check the exposure note

    Ports that should stay behind a firewall are called out.

  4. 4

    Browse by range

    Filter to well-known, registered or development ports.

Frequently asked questions

Database ports — 3306, 5432, 27017, 1433 — plus Redis on 6379, Memcached on 11211, SMB on 445 and RDP on 3389. All are scanned constantly, and several have no authentication by default.

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