404 error message This page could not be found

General
1 
I've been stuck on this screen for 7 days with the 404 error message
This page could not be found.

Can anyone help me?

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2

This 404 error can mean two different things. We just need to find out which one it is.

  1. An “App 404”: Your Next.js app is running, but it can’t find the specific page (e.g., your homepage).

  2. An “Environment 404”: The Firebase Studio preview window isn’t connected to your running app.

:detective: Let’s Find Out Which 404 It Is

Here is the most important test:

  1. In your Terminal, run your Next.js app. The most common command is:

    Bash

    npm run dev

  2. Wait for it to say “Ready” or “Compiled.”

  3. Have your Preview window open (with the 404 error).

  4. Refresh the Preview window.

  5. Now, look at your Terminal log immediately.

:thinking: What Did Your Terminal Do?

Scenario A: You see GET / 404 in your terminal

If new lines appeared in your terminal, especially something like GET / 404, this is great news!

  • What it means: The environment is working. The preview window is talking to your Next.js app. The problem is that Next.js itself is serving the 404.

  • The Fix: This almost always means you are missing your main homepage file.

    • Check your project: Do you have a file at src/app/page.tsx (or app/page.tsx if you aren’t using a src folder)?

    • If not, ask the AI agent: “Create a simple homepage component at src/app/page.tsx”

Scenario B: You see nothing new in your terminal

If you refreshed the preview and absolutely nothing new appeared in your terminal log, this means the environment is the problem.

  • What it means: The preview window is not correctly connected to your running app.

  • The Fix: The best fix is to “Hard Restart” the entire workspace VM. This clears any stuck processes.

    1. Press Cmd+Shift+P (on Mac) or Ctrl+Shift+P (on Windows/Linux) to open the command palette.1

    2. Type in Firebase Studio: Hard Restart.

    3. Select that option and press Enter.

    4. After it reboots, try npm run dev again.

What to Do Next

The fastest way to get this solved is to run npm run dev in your terminal and then paste the log here.

That log will tell us instantly if it’s Scenario A or B. We’re here to help!