Skip to content

`npm run dev` is a long-running program

New Course Coming Soon:

Get Really Good at Git

I got asked this question:

Each time I run npm run dev I get a different localhost port. First it was 3000. Then I ran it again and got port 3001. Then I ran it again and got port 3002. How do we force it to use port 3000?

When working on a website locally, you use the command npm run dev to start the development server.

This is a common practice in Web Development, and all tools seem to converge to this program, for example Astro and Next.js and many others.

Each time you run this command, it’s a long-running process. It does not end automatically

For example you run the Astro dev server, and it starts listening on port 3000:

Then you open another terminal and you run npm run dev again, this time you got the server running on port 3001:

So now you have the same app running on

http://localhost:3000

and

http://localhost:3001

You need to terminate both processes typing ctrl-c in your keyboard while in the terminal, so no process is keeping the 3000 port busy, and nothing appears in the browser when you try to open http://localhost:3000

Then you can run npm run dev again and it will automatically start on port 3000, because that’s free.

Any time you make a change in your project (for example because you have to npm install some package) you’re going to terminate the dev server with ctrl-c, then you start it again.

Are you intimidated by Git? Can’t figure out merge vs rebase? Are you afraid of screwing up something any time you have to do something in Git? Do you rely on ChatGPT or random people’s answer on StackOverflow to fix your problems? Your coworkers are tired of explaining Git to you all the time? Git is something we all need to use, but few of us really master it. I created this course to improve your Git (and GitHub) knowledge at a radical level. A course that helps you feel less frustrated with Git. Launching May 21, 2024. Join the waiting list!
→ Get my Node.js Handbook
→ Read my Node.js Tutorial on The Valley of Code

Here is how can I help you: