Next.js (Pages Router) quickstart

1. Install `hypertune`

Once you have a Next.js application (using the Pages Router) ready, install Hypertune's JavaScript SDK:

npm install hypertune

yarn add hypertune

pnpm add hypertune

2. Set environment variables

Define the following environment variables in your .env file:

NEXT_PUBLIC_HYPERTUNE_TOKEN=token
HYPERTUNE_FRAMEWORK=nextPages
HYPERTUNE_OUTPUT_DIRECTORY_PATH=generated

Replace token with your main project token which you can find in the Settings tab of your project.

3. Generate the client

Generate a type-safe client to access your flags by running:

npx hypertune

yarn hypertune

pnpm hypertune

4. Use the client

Add a new file called getHypertune.ts that exports a getHypertune function:

import { createSourceForServerOnly } from "@/generated/hypertune";

const hypertuneSource = createSourceForServerOnly({
  token: process.env.NEXT_PUBLIC_HYPERTUNE_TOKEN!,
});

export default async function getHypertune() {
  await hypertuneSource.initIfNeeded(); // Check for flag updates

  return hypertuneSource.root({
    args: {
      context: {
        environment: process.env.NODE_ENV,
        user: { id: "1", name: "Test", email: "hi@test.com" },
      },
    },
  });
}

To access flags in getServerSideProps during Server-side Rendering (SSR), use the getHypertune function:

import type {
  GetServerSideProps,
  InferGetServerSidePropsType,
} from "next";
import getHypertune from "@/lib/getHypertune";

type Props = { exampleFlag: boolean };

export const getServerSideProps = (async () => {
  const hypertune = await getHypertune();

  const exampleFlag = hypertune.exampleFlag({ fallback: false });

  return { props: { exampleFlag } };
}) satisfies GetServerSideProps<Props>;

export default function Page({
  exampleFlag,
}: InferGetServerSidePropsType<typeof getServerSideProps>) {
  return <div>Example Flag: {exampleFlag}</div>;
}

To access flags in getStaticProps during Static Site Generation (SSG) or Incremental Static Regeneration (ISR), use the getHypertune function:

import type {
  GetStaticProps,
  InferGetStaticPropsType,
} from "next";
import getHypertune from "@/lib/getHypertune";

type Props = { exampleFlag: boolean };

export const getStaticProps = (async () => {
  const hypertune = await getHypertune();

  const exampleFlag = hypertune.exampleFlag({ fallback: false });

  return { props: { exampleFlag }, revalidate: 10 };
}) satisfies GetStaticProps<Props>;

export default function Page({
  exampleFlag,
}: InferGetStaticPropsType<typeof getStaticProps>) {
  return <div>Example Flag: {exampleFlag}</div>;
}

To access flags in the browser during Client-side Rendering (CSR), first create a new <AppHypertuneProvider> component that wraps the generated <HypertuneProvider> component:

import { HypertuneProvider } from "@/generated/hypertune.react";

export default function AppHypertuneProvider({
  children,
}: {
  children: React.ReactNode;
}) {
  return (
    <HypertuneProvider
      createSourceOptions={{
        token: process.env.NEXT_PUBLIC_HYPERTUNE_TOKEN!,
      }}
      rootArgs={{
        context: {
          environment: process.env.NODE_ENV,
          user: { id: "1", name: "Test", email: "hi@test.com" },
        },
      }}
    >
      {children}
    </HypertuneProvider>
  );
}

Then wrap your app with the <AppHypertuneProvider> component in _app.tsx:

import type { AppProps } from "next/app";
import AppHypertuneProvider from "@/components/AppHypertuneProvider";
import "@/styles/globals.css";

export default function App({ Component, pageProps }: AppProps) {
  return (
    <AppHypertuneProvider>
      <Component {...pageProps} />
    </AppHypertuneProvider>
  );
}

Then use the generated useHypertune hook:

"use client";

import { useHypertune } from "@/generated/hypertune.react";

export default function ClientComponent() {
  const hypertune = useHypertune();

  const exampleFlag = hypertune.exampleFlag({ fallback: false });

  return <div>Example Flag: {String(exampleFlag)}</div>;
}

If you try accessing a flag immediately after the app loads, you'll get your hardcoded fallback value if the SDK hasn't initialized from Hypertune Edge yet. This can result in layout shift or UI flickers if the flag value changes when the SDK initializes.

To avoid this, wrap your pages with the generated <HypertuneHydrator> component:

import {
  GetServerSideProps,
  InferGetServerSidePropsType,
} from "next";
import {
  DehydratedState,
  RootArgs,
} from "@/generated/hypertune";
import { HypertuneHydrator } from "@/generated/hypertune.react";
import getHypertune from "@/lib/getHypertune";
import ClientComponent from "@/components/ClientComponent";

type Props = {
  serverDehydratedState: DehydratedState | null;
  serverRootArgs: RootArgs;
};

export const getServerSideProps = (async () => {
  const hypertune = await getHypertune();

  const serverDehydratedState = hypertune.dehydrate();
  const serverRootArgs = hypertune.getRootArgs();

  return { props: { serverDehydratedState, serverRootArgs } };
}) satisfies GetServerSideProps<Props>;

export default function Page({
  serverDehydratedState,
  serverRootArgs,
}: InferGetServerSidePropsType<typeof getServerSideProps>) {
  return (
    <HypertuneHydrator
      dehydratedState={serverDehydratedState}
      rootArgs={serverRootArgs}
    >
      <ClientComponent />
    </HypertuneHydrator>
  );
}

If you have a Content Security Policy, add the following URLs to the connect-src directive: https://edge.hypertune.com https://gcp.fasthorse.workers.dev

This lets the browser send analytics back to Hypertune so you can see how often different parts of your flag logic are evaluated, e.g. to see how many sessions fall into each targeting rule, as well as analytics for your events, A/B tests and machine learning loops.

To access flags in API Routes, use the getHypertune function:

import type { NextApiRequest, NextApiResponse } from "next";
import getHypertune from "@/lib/getHypertune";

type Data = { exampleFlag: boolean };

export default async function handler(
  req: NextApiRequest,
  res: NextApiResponse<Data>,
) {
  const hypertune = await getHypertune();

  const exampleFlag = hypertune.exampleFlag({ fallback: false });

  res.status(200).json({ exampleFlag });
}

To access flags in Middleware, use the getHypertune function:

import { NextFetchEvent, NextRequest } from "next/server";
import getHypertune from "@/lib/getHypertune";

export const config = {
  matcher: "/",
};

export async function middleware(
  req: NextRequest,
  event: NextFetchEvent,
) {
  const hypertune = await getHypertune();

  const exampleFlag = hypertune.exampleFlag({ fallback: false });
  console.log("Middleware Example Flag:", exampleFlag);

  event.waitUntil(hypertune.flushLogs());
}

5. (Optional) Include a build-time logic snapshot

To improve reliability, you can include a snapshot of your flag logic in the generated client at build time. The SDK will instantly initialize from the snapshot first before fetching the latest flag logic from Hypertune Edge.

Add the following environment variable to your .env file:

HYPERTUNE_INCLUDE_INIT_DATA=true

Then regenerate the client.

You can keep the snapshot fresh by setting up a webhook to regenerate the client on every Hypertune commit. In this case, you don't need to initialize from Hypertune Edge at all, eliminating network latency and bandwidth, improving both performance and efficiency.

6. (Optional) Use Vercel Edge Config

If your Next.js app is deployed on Vercel, you can use Edge Config to initialize the Hypertune SDK on the server with near-zero latency.

1. Install the integration

Go to the Hypertune page in the Vercel Integrations marketplace and click "Add Integration".
Select your Vercel team and project.
Continue and log into Hypertune.
Connect your Hypertune project to a new or existing Edge Config store. Copy the displayed environment variables for later. They contain your Hypertune Token, Edge Config Connection String and Edge Config Item Key.
Go to your Vercel dashboard and select the project you want to use the Hypertune integration with. Go to Settings > Environment Variables and add the following:
1. NEXT_PUBLIC_HYPERTUNE_TOKEN, set to your Hypertune Token
2. EDGE_CONFIG, set to your Edge Config Connection String
3. EDGE_CONFIG_HYPERTUNE_ITEM_KEY, set to your Edge Config Item Key

2. Use the integration

Pull the environment variables to your .env.development.local file by running:

vercel env pull .env.development.local

Install the @vercel/edge-config package:

npm install @vercel/edge-config

yarn add @vercel/edge-config

pnpm add @vercel/edge-config

Finally, update your getHypertune function to create an Edge Config client and pass it along with your Edge Config Item Key when creating the Hypertune source:

import { VercelEdgeConfigInitDataProvider } from "hypertune";
import { createClient } from "@vercel/edge-config";
import { createSourceForServerOnly } from "@/generated/hypertune";

const hypertuneSource = createSourceForServerOnly({
  token: process.env.NEXT_PUBLIC_HYPERTUNE_TOKEN!,
  initDataProvider:
    process.env.EDGE_CONFIG &&
    process.env.EDGE_CONFIG_HYPERTUNE_ITEM_KEY
      ? new VercelEdgeConfigInitDataProvider({
          edgeConfigClient: createClient(
            process.env.EDGE_CONFIG,
          ),
          itemKey: process.env.EDGE_CONFIG_HYPERTUNE_ITEM_KEY,
        })
      : undefined,
});

export default async function getHypertune() {
  await hypertuneSource.initIfNeeded(); // Check for flag updates

  return hypertuneSource.root({
    args: {
      context: {
        environment: process.env.NODE_ENV,
        user: { id: "1", name: "Test", email: "hi@test.com" },
      },
    },
  });
}

That's it

Now you can update the logic for exampleFlag from the Hypertune UI without updating your code or waiting for a new build, deployment or app release.

To add a new flag, create it in the Hypertune UI then regenerate the client.

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