By Dhanian

Artificial Intelligence is transforming how we interact with applications—and as a developer, I wanted to dive in and experience that firsthand. So I challenged myself to build a ChatGPT-like application using Next.js 15, TypeScript, TailwindCSS, and the OpenAI API.

Spoiler alert: it was surprisingly simple—and incredibly fun. Here's everything I learned, how I built it step-by-step, and what you should know if you're planning to build one too.

Why Build a ChatGPT Clone?

I chose this project because:

  • It's a real-world application of AI.
  • It helps you learn API integration, UI/UX design, state management, and async communication.
  • It’s highly customizable—you can turn it into a customer support bot, coding assistant, or even a SaaS tool.

Tech Stack Breakdown

Here’s what I used:

  • Next.js 15 (App Router): For server/client rendering and routing.
  • TailwindCSS: For quick and responsive UI styling.
  • OpenAI API: For chat capabilities.
  • TypeScript: For type safety and better dev experience.
  • React Hooks (useState, useEffect): To manage messages.

Project Architecture 

/chatgpt-clone
│
├── app/
│   ├── page.tsx      --> Main chat page
│   ├── api/
│   │   └── chat/route.ts  --> API route to OpenAI
│
├── components/
│   ├── ChatWindow.tsx
│   ├── Message.tsx
│
├── lib/
│   └── openai.ts     --> OpenAI config
│
├── styles/
│   └── globals.css

Step-by-Step Guide

1. Set Up the Next.js Project 

npx create-next-app@latest chatgpt-clone --typescript --app
cd chatgpt-clone
npm install openai tailwindcss

Set up Tailwind:

npx tailwindcss init -p

Edit tailwind.config.js and add paths to your files.

2. Create the Chat UI

/app/page.tsx:

"use client"
import { useState } from "react"

export default function HomePage() {
  const [messages, setMessages] = useState([{ role: "system", content: "How can I help you today?" }])
  const [input, setInput] = useState("")

  async function sendMessage() {
    const newMessages = [...messages, { role: "user", content: input }]
    setMessages(newMessages)
    setInput("")

    const res = await fetch("/api/chat", {
      method: "POST",
      body: JSON.stringify({ messages: newMessages }),
    })

    const data = await res.json()
    setMessages([...newMessages, data.reply])
  }

  return (
    <main className="min-h-screen p-6 bg-gray-100">
      <div className="max-w-2xl mx-auto bg-white p-4 rounded shadow">
        <div className="space-y-2 mb-4 h-[400px] overflow-y-auto">
          {messages.map((m, i) => (
            <div key={i} className={`text-${m.role === "user" ? "right" : "left"}`}>
              <p className={`text-sm p-2 rounded ${m.role === "user" ? "bg-blue-100" : "bg-gray-200"}`}>
                {m.content}
              p>
            div>
          ))}
        div>
        <div className="flex gap-2">
          <input
            className="flex-1 border p-2 rounded"
            value={input}
            onChange={(e) => setInput(e.target.value)}
          />
          <button onClick={sendMessage} className="bg-blue-500 text-white px-4 rounded">Sendbutton>
        div>
      div>
    main>
  )
}

3. Connect to OpenAI API

/app/api/chat/route.ts:

import { OpenAI } from "openai"

const openai = new OpenAI({
  apiKey: process.env.OPENAI_API_KEY,
})

export async function POST(req: Request) {
  const { messages } = await req.json()

  const response = await openai.chat.completions.create({
    model: "gpt-3.5-turbo",
    messages,
  })

  const reply = response.choices[0].message
  return Response.json({ reply })
}

Make sure you add your API key in .env.local:

OPENAI_API_KEY=your_key_here

What I Learned

  • Rate limits are a real concern when working with OpenAI’s free tier.
  • Streaming responses are the future—instant feedback improves UX.
  • Next.js App Router is incredibly clean for separating logic.
  • It’s super easy to build SaaS-like tools using AI APIs.

What’s Next?

  • Add authentication using NextAuth.
  • Save chat history to Supabase or MongoDB.
  • Enable response streaming for real-time interaction.
  • Upgrade to GPT-4 for premium power users.

Final Thoughts

Building this ChatGPT clone was one of the most exciting and practical mini-projects I’ve done. If you’re a developer looking to experiment with AI, there’s no better way to start.

Everything I Build Is Available Here:

Let’s build cool stuff together!