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:

.env

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:

lib/getHypertune.ts

import { createSourceForServerOnly } from '@/generated/hypertune'

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

export default async function getHypertune({
  isApiRoute = false,
}: {
  isApiRoute?: boolean
} = {}) {
  await hypertuneSource.initIfNeeded()

  hypertuneSource.setRemoteLoggingMode(
    isApiRoute ? 'normal' : 'off'
  )

  return hypertuneSource.root({
    args: {
      context: {
        environment: process.env.NODE_ENV,
        user: {
          id: 'e23cc9a8-0287-40aa-8500-6802df91e56a',
          name: 'Example User',
          email: '[email protected]',
        },
      },
    },
  })
}

To use flags in components, first create a new <AppHypertuneProvider> component that wraps the generated <HypertuneProvider> component:

components/AppHypertuneProvider.tsx

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: 'e23cc9a8-0287-40aa-8500-6802df91e56a',
            name: 'Example User',
            email: '[email protected]',
          },
        },
      }}
    >
      {children}
    </HypertuneProvider>
  )
}

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

pages/_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:

components/ExampleComponent.tsx

import { useHypertune } from '@/generated/hypertune.react'

export default function ExampleComponent() {
  const hypertune = useHypertune()

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

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

If you access 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 a flicker if the flag value changes when the SDK initializes.

To avoid this, wrap your page with the generated <HypertuneHydrator> and <HypertuneRootProvider> components, passing them dehydratedState and rootArgs from the server:

pages/index.tsx

import {
  GetServerSideProps,
  InferGetServerSidePropsType,
} from 'next'
import ExampleComponent from '@/components/ExampleComponent'
import { DehydratedState, RootArgs } from '@/generated/hypertune'
import {
  HypertuneHydrator,
  HypertuneRootProvider,
} from '@/generated/hypertune.react'
import getHypertune from '@/lib/getHypertune'

type Props = {
  dehydratedState: DehydratedState | null
  rootArgs: RootArgs
}

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

  const dehydratedState = hypertune.dehydrate()
  const rootArgs = hypertune.getRootArgs()

  return { props: { dehydratedState, rootArgs } }
}) satisfies GetServerSideProps<Props>

export default function Page({
  dehydratedState,
  rootArgs,
}: InferGetServerSidePropsType<typeof getServerSideProps>) {
  return (
    <HypertuneHydrator dehydratedState={dehydratedState}>
      <HypertuneRootProvider rootArgs={rootArgs}>
        <ExampleComponent />
      </HypertuneRootProvider>
    </HypertuneHydrator>
  )
}

Notes

Dynamic rendering: Using getServerSideProps makes your entire page dynamic. To use flags and run experiments on static pages (e.g. marketing pages), see the guide on using Hypertune on static pages.
Content Security Policy: If you have a CSP, add the following to your connect-src directive: https://edge.hypertune.com https://gcp.fasthorse.workers.dev. This enables reporting of flag evaluations, experiment exposures, and analytics events.

To use flags in getServerSideProps, use the getHypertune function. Include the <HypertuneClientLogger> component in your component tree, passing it the paths of any flags you use via the flagPaths prop. This ensures that flag evaluations and experiment exposures are logged on the client (in the browser):

pages/index.tsx

import {
  GetServerSideProps,
  InferGetServerSidePropsType,
} from 'next'
import { DehydratedState, RootArgs } from '@/generated/hypertune'
import {
  HypertuneClientLogger,
  HypertuneHydrator,
  HypertuneRootProvider,
} from '@/generated/hypertune.react'
import getHypertune from '@/lib/getHypertune'

type Props = {
  dehydratedState: DehydratedState | null
  rootArgs: RootArgs
  exampleFlag: boolean
}

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

  const dehydratedState = hypertune.dehydrate()
  const rootArgs = hypertune.getRootArgs()

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

  return { props: { dehydratedState, rootArgs, exampleFlag } }
}) satisfies GetServerSideProps<Props>

export default function Page({
  dehydratedState,
  rootArgs,
  exampleFlag,
}: InferGetServerSidePropsType<typeof getServerSideProps>) {
  return (
    <HypertuneHydrator dehydratedState={dehydratedState}>
      <HypertuneRootProvider rootArgs={rootArgs}>
        <div>
          Example Flag: {exampleFlag}
          <HypertuneClientLogger flagPaths={['exampleFlag']} />
        </div>
      </HypertuneRootProvider>
    </HypertuneHydrator>
  )
}

By default, remote logging is disabled on Next.js servers because prefetching and caching of pages and layouts can cause logs for flag evaluations, experiment exposures, and analytics events to differ from actual user behaviour. To ensure accuracy, remote logging is enabled by default on the client (in the browser) only. This is why you need to include the <HypertuneClientLogger> component in your component tree.

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

pages/api/example.ts

import { waitUntil } from '@vercel/functions'
import type { NextApiRequest, NextApiResponse } from 'next'
import getHypertune from '@/lib/getHypertune'

type ResponseData = { exampleFlag: boolean }

export default async function handler(
  req: NextApiRequest,
  res: NextApiResponse<ResponseData>
) {
  const hypertune = await getHypertune({ isApiRoute: true })

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

  waitUntil(hypertune.flushLogs())

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

Notes

Enable remote logging: By default, remote logging is disabled on Next.js servers because prefetching and caching of pages and layouts can cause logs for flag evaluations, experiment exposures, and analytics events to differ from actual user behaviour. To ensure accuracy, remote logging is enabled by default on the client (in the browser) only. However, since API Routes aren't subject to the same prefetching and caching patterns, remote logging is enabled for them by passing { isApiRoute: true } in the call to getHypertune.
Flush logs: waitUntil(hypertune.flushLogs()) ensures that logs are sent. Without this, logs may still flush in the background, but this isn't guaranteed in serverless environments like Vercel deployments.

To use flags in Middleware, use the getHypertune function:

middleware.ts

import { NextRequest } from 'next/server'
import getHypertune from '@/lib/getHypertune'

export const config = {
  matcher: '/(.*)',
}

export async function middleware(request: NextRequest) {
  const hypertune = await getHypertune()

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

  console.log(`Example Flag: ${exampleFlag}`)
}

Include the <HypertuneClientLogger> component in your component tree, passing it the paths of any flags you use via the flagPaths prop. This ensures that flag evaluations and experiment exposures are logged on the client (in the browser):

pages/index.tsx

import {
  GetServerSideProps,
  InferGetServerSidePropsType,
} from 'next'
import { DehydratedState, RootArgs } from '@/generated/hypertune'
import {
  HypertuneClientLogger,
  HypertuneHydrator,
  HypertuneRootProvider,
} from '@/generated/hypertune.react'
import getHypertune from '@/lib/getHypertune'

type Props = {
  dehydratedState: DehydratedState | null
  rootArgs: RootArgs
}

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

  const dehydratedState = hypertune.dehydrate()
  const rootArgs = hypertune.getRootArgs()

  return { props: { dehydratedState, rootArgs } }
}) satisfies GetServerSideProps<Props>

export default function Page({
  dehydratedState,
  rootArgs,
}: InferGetServerSidePropsType<typeof getServerSideProps>) {
  return (
    <HypertuneHydrator dehydratedState={dehydratedState}>
      <HypertuneRootProvider rootArgs={rootArgs}>
        <div>
          <h1>Home</h1>
          <HypertuneClientLogger flagPaths={['exampleFlag']} />
        </div>
      </HypertuneRootProvider>
    </HypertuneHydrator>
  )
}

The Hypertune Toolbar lets you view and override feature flags directly in your frontend. Follow the guide to add it to your app.

6. (Optional) Include a build-time 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.

7. (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:

lib/getHypertune.ts

import { createClient } from '@vercel/edge-config'
import { VercelEdgeConfigInitDataProvider } from 'hypertune'
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: 'e23cc9a8-0287-40aa-8500-6802df91e56a',
          name: 'Example User',
          email: '[email protected]',
        },
      },
    },
  })
}

Next steps

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.

PreviousNext.js (App Router) quickstart NextReact quickstart

Last updated 2 days ago

1. Install hypertune

2. Set environment variables

3. Generate the client

4. Use the client

5. (Optional) Add the Hypertune Toolbar

6. (Optional) Include a build-time snapshot

7. (Optional) Use Vercel Edge Config

1. Install the integration

2. Use the integration

Next steps

1. Install `hypertune`