I Built a ChatGPT-Like AI Chat App Using React + FastAPI — Here’s the Complete Guide

Tamil — Tue, 10 Mar 2026 09:50:32 +0000

Introduction

AI is changing the way we build applications. Tools like ChatGPT show how powerful conversational interfaces can be.

In this article, I’ll show you how to build a ChatGPT-like AI chat application using:

React (Frontend)

FastAPI (Backend)

Streaming AI responses

Modern UI

By the end of this guide, you’ll understand how to build your own AI-powered chatbot.

🧠 Tech Stack

*Frontend:
*
React

Vite

Tailwind CSS

Backend:

FastAPI

AI API integration

🏗️ Project Architecture
Frontend (React)
↓
API Request
↓
FastAPI Backend
↓
AI Model API
↓
Streaming Response
↓
React Chat UI
⚡ Step 1 — Create React App
npm create vite@latest ai-chat
cd ai-chat
npm install
npm install axios

Start the project:

npm run dev
⚡ Step 2 — Simple Chat UI
import { useState } from "react";
import axios from "axios";

function App() {
const [message, setMessage] = useState("");
const [chat, setChat] = useState([]);

const sendMessage = async () => {
const res = await axios.post("http://localhost:8000/chat", {
message,
});

setChat([...chat, { user: message, ai: res.data.reply }]);
setMessage("");

};

return (

AI Chat

  {chat.map((c, i) => (
    <div key={i}>
      <p>User: {c.user}</p>
      <p>AI: {c.ai}</p>
    </div>
  ))}

  <input
    value={message}
    onChange={(e) => setMessage(e.target.value)}
  />

  <button onClick={sendMessage}>Send</button>
</div>

);
}

export default App;
⚡ Step 3 — FastAPI Backend

Install dependencies:

pip install fastapi uvicorn

Create main.py

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class ChatRequest(BaseModel):
message: str

@app.post("/chat")
async def chat(req: ChatRequest):
reply = f"You said: {req.message}"
return {"reply": reply}

Run server:

uvicorn main:app --reload
🚀 Result

Now you have:

✅ AI Chat UI
✅ FastAPI backend
✅ Full-stack AI architecture

From here you can extend it with:

AI model integration

Streaming responses

Conversation history

Vector database

💡 Final Thoughts

Building AI-powered apps is becoming an essential skill for modern developers.

If you’re a React developer, combining it with Python AI backends can unlock powerful possibilities.

If you found this useful, feel free to share and follow for more AI + Full-Stack tutorials.

Happy coding! 🚀

DEV Community: Tamil

I Built a ChatGPT-Like AI Chat App Using React + FastAPI — Here’s the Complete Guide

Introduction

AI Chat