Localhost Port Tester | localhost:3000, 8080, 5173 Guide

Look up what runs on any localhost port, open it in one click, and understand localhost vs 127.0.0.1. Covers 20+ dev ports including React, Vite, Ollama, Python, and databases. Designed specifically for developers and professionals, this free online networking runs entirely in your browser to process tasks quickly and securely. Enjoy unlimited usage with no data tracking and no registration required.

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Port Number

Quick:

localhost

hostname

Hostname that resolves to the loopback address. Always refers to your own machine.

127.0.0.1

IPv4 loopback

IPv4 loopback address. Traffic never leaves your machine - it goes straight back to you.

::1

IPv6 loopback

IPv6 equivalent of 127.0.0.1. Used when the system defaults to IPv6.

0.0.0.0

bind-all

Not an address you connect to. A server bound here accepts connections from any interface, including external ones.

Common Development Ports

40 ports

3000

Grafana

Grafana dashboards and observability (often 3000 or 3001)

3001

React (fallback) / Remix

Used when port 3000 is occupied; also Remix dev server default

4200

Angular CLI

Default development server for Angular projects

5173

Vite

Default dev server for Vite-powered projects (Vue, React, Svelte, Vanilla)

5174

Vite (second instance)

Vite fallback port when 5173 is occupied

3333

AdonisJS

Default port for AdonisJS Node.js framework

4321

Astro

Default dev server port for Astro static site builder

5000

Flask / .NET Kestrel / SvelteKit

Default for Flask (Python), .NET Kestrel, and SvelteKit preview

8000

FastAPI / Django

FastAPI and Django development server default port

8080

Ollama Web UI / Open WebUI

Default port for Open WebUI (Ollama frontend)

9000

PHP / SonarQube / Vite preview

PHP built-in server, SonarQube quality gate, and Vite build preview

9229

Node.js Debugger

Node.js --inspect debug protocol (Chrome DevTools attach)

24678

Vite HMR

Vite Hot Module Replacement WebSocket port

4000

GraphQL / Phoenix (Elixir)

Common for GraphQL servers, Phoenix framework, and backend APIs

1337

Strapi CMS

Default port for Strapi headless CMS development server

8888

Jupyter Notebook / Lab

Jupyter Notebook and JupyterLab development server

11434

Ollama

Default port for the Ollama local AI/LLM model server

7860

Gradio

Default port for Gradio ML model web interfaces

8501

Streamlit

Default port for Streamlit Python data apps

6006

TensorBoard

TensorBoard training and visualization tool

11435

Ollama (alt)

Alternative port when Ollama 11434 is in use

3306

MySQL / MariaDB

Default MySQL and MariaDB database port

5432

PostgreSQL

Default PostgreSQL relational database port

27017

MongoDB

Default MongoDB document database port

6379

Redis

Default Redis in-memory cache and message broker port

9200

Elasticsearch

Default Elasticsearch HTTP REST API port

5984

CouchDB

Default CouchDB NoSQL document database port

8529

ArangoDB

Default ArangoDB multi-model database port

6432

PgBouncer

Default PgBouncer PostgreSQL connection pooler port

1433

SQL Server (MSSQL)

Microsoft SQL Server database default port

2375

Docker (no TLS)

Docker daemon unencrypted REST API

2376

Docker (TLS)

Docker daemon encrypted REST API

8001

Kubernetes Dashboard / Kong

Kubernetes Dashboard and Kong API Gateway admin

9090

Prometheus

Prometheus metrics server and alerting

9411

Zipkin

Zipkin distributed tracing UI

16686

Jaeger UI

Jaeger distributed tracing dashboard

8161

ActiveMQ Admin

ActiveMQ message broker admin console

5672

RabbitMQ

RabbitMQ AMQP message broker

15672

RabbitMQ Management

RabbitMQ web management console

9092

Apache Kafka

Kafka broker client listener port

Common localhost Errors & Fixes

ERR_CONNECTION_REFUSED

Nothing is running on that port

Fix: Start your dev server (npm run dev, python manage.py runserver, etc.)

EADDRINUSE / port already in use

Another process is already bound to this port

Fix: Kill the conflicting process or start the server on a different port (PORT=3001 npm run dev)

ERR_CONNECTION_TIMED_OUT

Firewall or OS silently dropping connection attempts

Fix: Check local firewall rules; ensure the server binds to 0.0.0.0 or 127.0.0.1

ECONNREFUSED (Node.js runtime)

Server process is not running at all

Fix: Start the server and watch console output for startup errors

ERR_LOCALHOST_MISMATCH

Server bound only to IPv6 (::1) but browser connects via IPv4 (127.0.0.1)

Fix: Bind server to 0.0.0.0 or explicitly use 127.0.0.1 in the URL

About Localhost Port Tester

Type any port number to instantly see what service runs there. Covers 40+ common development ports for React, Vite, Angular, Ollama, Python, databases, DevOps tools, and more - plus a plain-English explanation of localhost vs 127.0.0.1.

Key Features

Instant lookup as you type - no button needed
Reference table of 40+ popular development server ports
One-click links to open http://localhost:[port] in your browser
Explains localhost, 127.0.0.1, ::1, and 0.0.0.0 differences
Common error codes with actionable fixes
Covers AI tools: Ollama (11434), Gradio (7860), Streamlit (8501)

Use Cases

Find what runs on localhost:3000, 8080, 5173, or 11434
Debug ERR_CONNECTION_REFUSED on a local development server
Check what port Ollama, Jupyter, or Streamlit uses
Understand the difference between localhost and 127.0.0.1

Related Keywords

localhost

localhost:3000

localhost:8080

localhost:5173

127.0.0.1 meaning

ollama port

localhost port checker

what is localhost

local development ports

localhost:8080

http://localhost:3000

http://localhost:5173

Privacy & Security

All processing happens locally in your browser. Your data never leaves your computer, ensuring complete privacy and security.

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Frequently asked questions

What is Localhost Port Tester used for?

Look up what runs on any localhost port, open it in one click, and understand localhost vs 127.0.0.1. Covers 20+ dev ports including React, Vite, Ollama, Python, and databases.

Is Localhost Port Tester free to use?

Yes. Localhost Port Tester is completely free with no usage limits, and there is no paid tier required to use it.

Do I need an account to use Localhost Port Tester?

No. Localhost Port Tester works immediately in your browser with no signup, login, or email address required.

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