Build a Guestbook with Next.js and Supabase

Build and deploy a guestbook app using Next.js, Supabase, shadcn/ui, and Vercel.

Introduction

30 Second Summary

Every developer tool starts with the same challenge: keeping user data private while making it instant to access. Whether it's a project tracker or an AI assistant, you need a secure workspace that belongs to each user alone.

In this project, you will build an authenticated developer dashboard called "Context-Engine" using Next.js, Supabase, and shadcn/ui. You will wire up email authentication, create a database with Row Level Security, and build a clean UI for managing project blueprints.

What You'll Build

After signing up, you land on a personal dashboard where you can create project entries with a name, description, and tech stack, then click into any project to view its full details.

By the end of this project, you'll have:

  • Email authentication that lets you sign up, sign in, and sign out of your personal workspace.
  • A project dashboard displaying only your entries, secured by Row Level Security so no other user can see your data.
  • A create form powered by Server Actions that inserts a project into your database and immediately shows it on the dashboard.
  • A detail page for each project with its own URL, showing the full name, description, tech stack, and creation date.
  • Secret Mission: Add a delete button with a confirmation dialog to remove projects you no longer need.

Are there any prerequisites?

You will need a free Supabase account, a free Vercel account, Node.js v24 installed on your machine, and Cursor installed as your code editor. Step 1 walks you through confirming each of these.

Secret mission

Add Delete with Confirmation

Your dashboard lets you create projects, but what about removing ones you no longer need? In this stretch challenge, you will add a delete button with a confirmation dialog to prevent accidental deletions. This introduces client-side interactivity alongside Server Actions, teaching you the boundary between Client and Server Components.

Clean Up Your Resources

Clean Up Your Resources

Decide whether to keep your resources running, pause them to come back later, or delete them entirely. This project runs on the Supabase free tier, so there are no ongoing costs while your project exists.

Resources you used:

  • Supabase project (free tier): includes the database, auth users, and projects table.
  • Local Next.js project files in the context-engine folder on your Desktop.

Keep everything running

No action needed. Choose this if you are still actively building or plan to continue with the next project in this series.

  • Your Supabase project stays active on the free tier indefinitely.
  • Your local context-engine folder remains on your Desktop.
  • The dev server continues running at http://localhost:3000 until you stop it with Ctrl+C in the terminal.

Pause - I'll come back to this later

Shut down running processes to free up memory and your free-tier project slot, but keep your files so you can resume later.

  • Press Ctrl+C in the terminal where npm run dev is running to stop the local dev server.
  • In the Supabase Dashboard, select your project, go to Settings, then General, and click Pause project. This frees up your free-tier project slot while preserving all your data.
  • Your local context-engine folder stays on your Desktop for when you return.

Delete - I don't want to use this again

Remove all project resources and start fresh. This cannot be undone.

  • Press Ctrl+C in the terminal where npm run dev is running to stop the local dev server.
  • In the Supabase Dashboard, select your project, go to Settings, then General. Scroll to the bottom and click Delete project. Confirm the deletion when prompted.
  • Delete the local project folder. On macOS/Linux, run:
rm -rf ~/Desktop/context-engine

On Windows, run:

rmdir /s /q $env:USERPROFILE\Desktop\context-engine

That's a Wrap!

That's a Wrap!

Nice work! You just built Context-Engine, a full-stack authenticated dashboard where users can securely manage their own project blueprints.

You've learned how to:

  • Build a full-stack authenticated Next.js application using the Supabase template, with cookie-based sign-up, sign-in, and sign-out wired end-to-end.
  • Create a PostgreSQL database table with Row Level Security policies that enforce per-user data isolation so no one else can read your projects.
  • Implement Server Actions to securely insert data without exposing API endpoints, and build a polished dashboard UI with shadcn/ui components and dynamic routes for individual project pages.
  • Secret Mission: Added a delete flow with a confirmation Dialog, learning the Client Component boundary pattern for mixing interactivity with Server Actions.

Ready to quiz yourself?