localhost:3333: what runs on it and how to open it
Port 3333 is the default dev server port of AdonisJS. How to start it and fix errors.
Open this address: http://localhost:3333This opens on your own computer. It only works if the program is running.
localhost:3333 is where AdonisJS apps usually run while you develop. The PORT value in the .env file decides the number.
What runs on localhost:3333
- AdonisJS apps during development
- Any Node app that uses PORT=3333
Commands to start and test port 3333
node ace serve --watchPORT=3334 node ace serve --watchFind what is using port 3333
Run these in a terminal on your computer. Nothing is sent to this site.
If localhost:3333 will not open
- The app starts on a different port
- The PORT value in your .env file wins. Check it and read the address the terminal prints.
- Port 3333 is already in use
- Another program is on this port. Find it with the tool below and stop it, or start yours on another port.
- This site can’t be reached (ERR_CONNECTION_REFUSED)
- The program is not running. Start it and keep that terminal open. See the full checklist.
- Works on your computer, not on your phone
- Start the server on all network addresses and use your computer’s IP address. See how to open localhost from your phone.
Other ports like 3333
| Port | Usually used by |
|---|---|
| localhost:3000 | React, Next.js, Express |
| localhost:5173 | Vite dev server |
| localhost:4200 | Angular dev server |
| localhost:5000 | Flask |
| localhost:8000 | Django, PHP, Python |
| localhost:8080 | Tomcat, Spring Boot, Docker |
| localhost:8888 | Jupyter Notebook |
Questions about localhost:3333
- Where is the port set?
- In the .env file as PORT=3333.
- Is localhost:3333 safe?
- Yes, as long as it stays on localhost. Only your own computer can reach it. It becomes reachable from other devices only if you start the program on 0.0.0.0 or your computer's IP address. Do not put development or admin tools on the public internet.
- Can I use a different port instead of 3333?
- Yes. Most programs let you choose the port with a setting or a command option. Pick a free port above 1024 and open that number instead.
- How do I check what is using port 3333?
- Use the port checker on this page. It shows the command for Windows, macOS and Linux and does not send anything to this site.
- Can I open localhost:3333 from my phone?
- Yes, if both are on the same Wi-Fi. Start the program so it listens on all addresses, then open your computer's IP address with the port on the phone. A firewall on the computer can still block it.
Free tools that help
- Common ports listSearch a list of common TCP and UDP port numbers: SSH 22, HTTP 80, HTTPS 443, MySQL 3306, PostgreSQL 5432 and more, with dev server ports.