Next.js

PostHog makes it easy to get data about traffic and usage of your Next.js app. Integrating PostHog into your site enables analytics about user behavior, custom events capture, session recordings, feature flags, and more.

This guide walks you through integrating PostHog into your Next.js app using the React and the Node.js SDKs.

You can see a working example of this integration in our Next.js demo app.

Next.js has both client and server-side rendering, as well as pages and app routers. We'll cover all of these options in this guide.

Prerequisites

To follow this guide along, you need:

1. A PostHog instance (either Cloud or self-hosted)
2. A Next.js application

Beta: integration via LLM

Install PostHog for Next.js in seconds with our wizard by running this prompt with LLM coding agents like Cursor and Bolt, or by running it in your terminal.

npx -y @posthog/wizard@latest --region us

Or, to integrate manually, continue with the rest of this guide.

Client-side setup

Install posthog-js using your package manager:

npm install --save posthog-js

yarn add posthog-js

pnpm add posthog-js

bun add posthog-js

Add your environment variables to your .env.local file and to your hosting provider (e.g. Vercel, Netlify, AWS). You can find your project API key in your project settings.

NEXT_PUBLIC_POSTHOG_KEY=<ph_project_api_key>
NEXT_PUBLIC_POSTHOG_HOST=https://us.i.posthog.com

These values need to start with NEXT_PUBLIC_ to be accessible on the client-side.

Integration

Next.js provides the instrumentation-client.ts|js file for client-side setup. Add it to the root of your Next.js app (for both app and pages router) and initialize PostHog in it like this:

import posthog from 'posthog-js'

posthog.init(process.env.NEXT_PUBLIC_POSTHOG_KEY, {
  api_host: process.env.NEXT_PUBLIC_POSTHOG_HOST,
  defaults: '2026-01-30'
});

import posthog from 'posthog-js'

posthog.init(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  api_host: process.env.NEXT_PUBLIC_POSTHOG_HOST,
  defaults: '2026-01-30'
});

Accessing PostHog

Once initialized in instrumentation-client.js|ts, import posthog from posthog-js anywhere and call the methods you need on the posthog object.

'use client'
import posthog from 'posthog-js'

export default function Home() {
  return (
    <div>
      <button onClick={() => posthog.capture('test_event')}>
        Click me for an event
      </button>
    </div>
  );
}

Using React hooks

The React feature flag hooks work automatically when PostHog is initialized via instrumentation-client.ts. The hooks use the initialized posthog-js singleton:

'use client'
import { useFeatureFlagEnabled } from 'posthog-js/react'

export default function FeatureComponent() {
  const showNewFeature = useFeatureFlagEnabled('new-feature')

  return showNewFeature ? <NewFeature /> : <OldFeature />
}

Usage

See the React SDK docs for examples of how to use:

• posthog-js functions like custom event capture, user identification, and more.
• Feature flags including variants and payloads.

You can also read the full posthog-js documentation for all the usable functions.

Server-side analytics

Next.js enables you to both server-side render pages and add server-side functionality. To integrate PostHog into your Next.js app on the server-side, you can use the Node SDK.

First, install the posthog-node library:

npm install posthog-node --save

yarn add posthog-node

pnpm add posthog-node

bun add posthog-node

Router-specific instructions

// app/posthog.js
import { PostHog } from 'posthog-node'

export default function PostHogClient() {
  const posthogClient = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY, {
    host: process.env.NEXT_PUBLIC_POSTHOG_HOST,
    flushAt: 1,
    flushInterval: 0
  })
  return posthogClient
}

import Link from 'next/link'
import PostHogClient from '../posthog'

export default async function About() {

  const posthog = PostHogClient()
  const flags = await posthog.getAllFlags(
    'user_distinct_id' // replace with a user's distinct ID
  );
  await posthog.shutdown()

  return (
    <main>
      <h1>About</h1>
      <Link href="/">Go home</Link>
      { flags['main-cta'] &&
        <Link href="http://posthog.com/">Go to PostHog</Link>
      }
    </main>
  )
}

// pages/posts/[id].js
import { useContext, useEffect, useState } from 'react'
import { getServerSession } from "next-auth/next"
import { PostHog } from 'posthog-node'

export default function Post({ post, flags }) {
  const [ctaState, setCtaState] = useState()

  useEffect(() => {
    if (flags) {
      setCtaState(flags['blog-cta'])
    }
  })

  return (
    <div>
      <h1>{post.title}</h1>
      <p>By: {post.author}</p>
      <p>{post.content}</p>
      {ctaState &&
        <p><a href="/">Go to PostHog</a></p>
      }
      <button onClick={likePost}>Like</button>
    </div>
  )
}

export async function getServerSideProps(ctx) {

  const session = await getServerSession(ctx.req, ctx.res)
  let flags = null

  if (session) {
    const client = new PostHog(
      process.env.NEXT_PUBLIC_POSTHOG_KEY,
      {
        host: process.env.NEXT_PUBLIC_POSTHOG_HOST,
      }
    )

    flags = await client.getAllFlags(session.user.email);
    client.capture({
      distinctId: session.user.email,
      event: 'loaded blog article',
      properties: {
        $current_url: ctx.req.url,
      },
    });

    await client.shutdown()
  }

  const { posts } = await import('../../blog.json')
  const post = posts.find((post) => post.id.toString() === ctx.params.id)
  return {
    props: {
      post,
      flags
    },
  }
}

Server-side configuration

Next.js overrides the default fetch behavior on the server to introduce their own cache. PostHog ignores that cache by default, as this is Next.js's default behavior for any fetch call.

You can override that configuration when initializing PostHog, but make sure you understand the pros/cons of using Next.js's cache and that you might get cached results rather than the actual result our server would return. This is important for feature flags, for example.

posthog.init(process.env.NEXT_PUBLIC_POSTHOG_KEY, {
  // ... your configuration
  fetch_options: {
    cache: 'force-cache', // Use Next.js cache
    next_options: {       // Passed to the `next` option for `fetch`
      revalidate: 60,     // Cache for 60 seconds
      tags: ['posthog'],  // Can be used with Next.js `revalidateTag` function
    },
  }
})

Configuring a reverse proxy to PostHog

To improve the reliability of client-side tracking and make requests less likely to be intercepted by tracking blockers, you can setup a reverse proxy in Next.js. Read more about deploying a reverse proxy using Next.js rewrites, Next.js middleware, and Vercel rewrites.

Further reading

• How to set up Next.js analytics, feature flags, and more
• How to set up Next.js pages router analytics, feature flags, and more
• How to set up Next.js A/B tests