Use Genkit in a Next.js app

This page shows how you can use Genkit flows as server actions in your Next.js apps.

Before you begin

You should be familiar with Genkit's concept of flows, and how to write them.

Create a Next.js project

If you don't already have a Next.js project that you want to add generative AI features to, you can create one for the purpose of following along with this page:

npx create-next-app@latest

Install Genkit dependencies

Install the Genkit dependencies into your Next.js app, the same way you would for any Genkit project:

1. Install the core Genkit library:

   npm i --save genkit

2. Install at least one model plugin.

   For example, to use Google AI:

   npm i --save @genkit-ai/googleai

   Or to use Vertex AI:

   npm i --save @genkit-ai/vertexai

3. If you didn't install the Genkit CLI globally, you can install it as a development dependency. The tsx tool is also recommended, as it makes testing your code more convenient. Both of these dependencies are optional, however.

   npm i --save-dev genkit-cli tsx

Define Genkit flows

Create a new file in your Next.js project to contain your Genkit flows: for example, src/app/genkit.ts. This file can contain your flows without modification; however, because you can only run flows from a server backend, you must add the 'use server' directive to the top of the file.

For example:

'use server';

import { gemini15Flash, googleAI } from "@genkit-ai/googleai";
import { genkit, z } from "genkit";

const ai = genkit({
  plugins: [googleAI()],
  model: gemini15Flash,
});

export const menuSuggestionFlow = ai.defineFlow(
  {
    name: "menuSuggestionFlow",
    inputSchema: z.string(),
    outputSchema: z.string(),
  },
  async (restaurantTheme) => {
    const { text } = await ai.generate({
      model: gemini15Flash,
      prompt: `Invent a menu item for a ${restaurantTheme} themed restaurant.`,
    });
    return text;
  }
);

Call your flows

Now, in your frontend code, you can import your flows and call them as server actions.

For example:

'use client';

import { menuSuggestionFlow } from './genkit';
import { useState } from 'react';

export default function Home() {
  const [menuItem, setMenuItem] = useState<string>('');

  async function getMenuItem(formData: FormData) {
    const theme = formData.get('theme')?.toString() ?? '';
    const suggestion = await menuSuggestionFlow(theme);
    setMenuItem(suggestion);
  }

  return (
    <main>
      <form action={getMenuItem}>
        <label htmlFor="theme">
          Suggest a menu item for a restaurant with this theme:{' '}
        </label>
        <input type="text" name="theme" id="theme" />
        <br />
        <br />
        <button type="submit">Generate</button>
      </form>
      <br />
      <pre>{menuItem}</pre>
    </main>
  );
}

Test your app locally

If you want to run your app locally, you need to make credentials for the model API service you chose available.

Then, run your app locally as normal:

npm run dev

All of Genkit's development tools continue to work as normal. For example, to load your flows in the developer UI:

npx genkit start -- npx tsx --watch src/app/genkit.ts

Deploy your app

When you deploy your app, you will need to make sure the credentials for any external services you use (such as your chosen model API service) are available to the deployed app. See the following pages for information specific to your chosen deployment platform:

• Cloud Functions for Firebase
• Cloud Run
• Other Node.js platforms