Build an AI-Powered Web App with GPT-5 and Next.js in 30 Minutes

Building AI-powered applications no longer requires weeks of setup or a large engineering team. With GPT-5 and Next.js, you can create a fast, scalable, and intelligent web app in under 30 minutes.

This guide walks you through the core steps to launch a simple AI-powered web app that takes user input and returns AI-generated responses.

What You’ll Build

A simple web app that:

• Uses Next.js for the frontend and backend
• Connects to GPT-5 via API
• Accepts user input and returns AI-generated output
• Is easy to extend into chatbots, tools, or SaaS products

Tech Stack

• Next.js (App Router)
• GPT-5 API
• React
• Node.js
• Tailwind CSS (optional)

Step 1: Create a Next.js App (5 Minutes)

Run the following commands:

npx create-next-app ai-web-app
cd ai-web-app
npm run dev

Your app will be running at:
http://localhost:3000

Step 2: Install Required Dependencies (2 Minutes)

Install the OpenAI SDK:

npm install openai

Step 3: Set Up Environment Variables (2 Minutes)

Create a .env.local file in the root of your project:

OPENAI_API_KEY=your_api_key_here

Step 4: Create an API Route for GPT-5 (8 Minutes)

Create a new file at:

/app/api/ai/route.js

Add the following code:

import OpenAI from "openai";
import { NextResponse } from "next/server";

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

export async function POST(req) {
  const { prompt } = await req.json();

  const response = await openai.responses.create({
    model: "gpt-5",
    input: prompt,
  });

  return NextResponse.json({
    result: response.output_text,
  });
}

This API route securely communicates with GPT-5 and keeps your API key hidden from the client.

Step 5: Build the Frontend UI (10 Minutes)

Edit the file:

app/page.js

Add the following code:

"use client";

import { useState } from "react";

export default function Home() {

  const [input, setInput] = useState("");

  const [output, setOutput] = useState("");

  const [loading, setLoading] = useState(false);

async function handleSubmit() {

    setLoading(true);

    const res = await fetch("/api/ai", {

      method: "POST",

      headers: { "Content-Type": "application/json" },

      body: JSON.stringify({ prompt: input }),

    });

    const data = await res.json();

    setOutput(data.result);

    setLoading(false);

  }

return (

    <main style={{ padding: "40px", maxWidth: "600px", margin: "auto" }}>

      <h1>AI-Powered App with GPT-5</h1>

  &lt;textarea
    value={input}
    onChange={(e) =&gt; setInput(e.target.value)}
    placeholder="Ask something..."
    rows={4}
    style={{ width: "100%", marginTop: "10px" }}
  /&gt;

  &lt;button onClick={handleSubmit} style={{ marginTop: "10px" }}&gt;
    {loading ? "Thinking..." : "Generate"}
  &lt;/button&gt;

  {output &amp;&amp; (
    &lt;div style={{ marginTop: "20px" }}&gt;
      &lt;strong&gt;Response:&lt;/strong&gt;
      &lt;p&gt;{output}&lt;/p&gt;
    &lt;/div&gt;
  )}
&lt;/main&gt;



    

    




);

}

Step 6: Test Your App (3 Minutes)

• Enter a question or prompt
• Click Generate
• Receive a GPT-5-powered response instantly

You now have a fully functional AI-powered web app.

Why This Stack Works So Well

• Next.js handles frontend and backend in a single project
• GPT-5 delivers advanced reasoning and natural language responses
• API routes keep your API key secure
• Scalable by default for SaaS or production use

Ideas to Extend This App

• AI chatbot
• Resume or cover-letter generator
• Study assistant
• Startup idea validator
• Content writing tool

Final Thoughts

You don’t need complex infrastructure to build powerful AI products. With GPT-5 and Next.js, you can prototype, test, and launch AI-driven web apps faster than ever.

From here, you can add authentication, databases, payment systems, or deploy to Vercel in minutes.

Build fast. Iterate smarter. Let AI do the heavy lifting.