Localhost Checkpoint

What this is

Localhost is the learner's private preview of the project.

This checkpoint confirms the project can run before any real feature work starts.

Why it matters

If localhost is broken, every next step becomes confusing.

Fix setup first. Do not build on top of a project that cannot open in the browser.

What to do

Open the terminal inside the project folder.

First check that the folder has package.json.

Then run:

npm install
npm run dev

Keep the terminal open.

Open:

http://localhost:3000

The learner must see a page in the browser before continuing.

Do not ask AI to build the first section yet. This page is only for proving the project can run.

If there is an error, paste the exact message into AI:

My project does not run on localhost.

Command I ran:
[paste command]

Error:
[paste full error]

Expected:
I should be able to open http://localhost:3000

Fix this one step at a time.

When localhost works, keep the terminal running. You will use the browser preview in the next step.

Common mistakes

• Running commands in the wrong folder.
• Closing the terminal that is running npm run dev.
• Opening localhost before install finishes.
• Ignoring an error and asking AI to build features anyway.
• Moving to the build step before the browser preview works.