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Integration Nextjs Pages Router

PostHogOfficialCreated by PostHog

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  • Tool integration
  • Software development
  • MIT
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From the author

PostHog integration for Next.js Pages Router applications
— the description by PostHog

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a systematic approach to integrating PostHog into Next.js projects that utilize the Pages Router architecture. It covers client-side initialization, server-side tracking, user identification, and error tracking. The guide emphasizes best practices such as using environment variables, avoiding hardcoded keys, and maintaining clean event-handling logic by avoiding unnecessary useEffect hooks.

What it does

  • Provides a step-by-step workflow for PostHog setup
  • Demonstrates client-side initialization via instrumentation-client.ts
  • Shows how to implement server-side tracking for API routes
  • Guides user identification during authentication flows
  • Includes patterns for error tracking and feature flag usage
  • Offers a reference project structure for Pages Router applications

When to use it

  • When adding product analytics to a new or existing Next.js Pages Router application
  • When needing to track user behavior across both client and server boundaries
  • When implementing feature flags or session replay in a Next.js environment
  • When you need to ensure consistent event tracking patterns across your codebase

Advantages

  • Follows established patterns for Next.js Pages Router
  • Ensures secure handling of project tokens via environment variables
  • Promotes clean React code by discouraging misuse of useEffect
  • Supports both client-side and server-side event correlation

Usage examples

“How do I initialize PostHog in my Next.js Pages Router app?”
The skill directs you to create an instrumentation-client.ts file and configure it using your project token from environment variables.
“Where should I place event tracking code for user actions?”
The skill advises placing capture calls directly within event handlers rather than inside useEffect hooks.
“How do I track events on the server side in my API routes?”
The skill provides a pattern for using a server-side PostHog client to capture events in files located within the pages/api/ directory.
“How do I identify users after they log in?”
The skill shows how to use the posthog.identify() method within your authentication context or login logic.

Install

  1. Download the skill as a ZIP:

    https://autogineer.com/agent-skills/posthog/integration-nextjs-pages-router/download

  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip integration-nextjs-pages-router.zip -d .agents/skills

Documentation by PostHog

PostHog integration for Next.js Pages Router

This skill helps you add PostHog analytics to Next.js Pages Router applications.

Workflow

Follow these steps in order to complete the integration:

  1. basic-integration-1.0-begin.md - PostHog Setup - Begin ← Start here

  2. basic-integration-1.1-edit.md - PostHog Setup - Edit

  3. basic-integration-1.2-revise.md - PostHog Setup - Revise

  4. basic-integration-1.3-conclude.md - PostHog Setup - Conclusion

Reference files

  • references/EXAMPLE.md - Next.js Pages Router example project code

  • references/next-js.md - Next.js - docs

  • references/identify-users.md - Identify users - docs

  • references/basic-integration-1.0-begin.md - PostHog setup - begin

  • references/basic-integration-1.1-edit.md - PostHog setup - edit

  • references/basic-integration-1.2-revise.md - PostHog setup - revise

  • references/basic-integration-1.3-conclude.md - PostHog setup - conclusion

The example project shows the target implementation pattern. Consult the documentation for API details.

Key principles

  • Environment variables: Always use environment variables for PostHog keys. Never hardcode them.

  • Minimal changes: Add PostHog code alongside existing integrations. Don't replace or restructure existing code.

  • Match the example: Your implementation should follow the example project's patterns as closely as possible.

Framework guidelines

  • For Next.js 15.3+, initialize PostHog in instrumentation-client.ts for the simplest setup

  • For feature flags, use useFeatureFlagEnabled() or useFeatureFlagPayload() hooks - they handle loading states and external sync automatically

  • Add analytics capture in event handlers where user actions occur, NOT in useEffect reacting to state changes

  • Do NOT use useEffect for data transformation - calculate derived values during render instead

  • Do NOT use useEffect to respond to user events - put that logic in the event handler itself

  • Do NOT use useEffect to chain state updates - calculate all related updates together in the event handler

  • Do NOT use useEffect to notify parent components - call the parent callback alongside setState in the event handler

  • To reset component state when a prop changes, pass the prop as the component's key instead of using useEffect

  • useEffect is ONLY for synchronizing with external systems (non-React widgets, browser APIs, network subscriptions)

Identifying users

Identify users during login and signup events. Refer to the example code and documentation for the correct identify pattern for this framework. If both frontend and backend code exist, pass the client-side session and distinct ID using X-POSTHOG-DISTINCT-ID and X-POSTHOG-SESSION-ID headers to maintain correlation.

Error tracking

Add PostHog error tracking to relevant files, particularly around critical user flows and API boundaries.

Files

references/EXAMPLE.md

PostHog Next.js Pages Router Example Project

Repository: https://github.com/PostHog/context-mill Path: basics/next-pages-router

README.md

PostHog Next.js pages router example

This is a Next.js Pages Router example demonstrating PostHog integration with product analytics, session replay, feature flags, and error tracking.

Features

  • Product Analytics: Track user events and behaviors

  • Session Replay: Record and replay user sessions

  • Error Tracking: Capture and track errors

  • User Authentication: Demo login system with PostHog user identification

  • Server-side & Client-side Tracking: Examples of both tracking methods

  • Reverse Proxy: PostHog ingestion through Next.js rewrites

Getting Started

1. Install Dependencies
npm install
# or
pnpm install
2. Configure Environment Variables

Create a .env.local file in the root directory:

NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN=your_posthog_project_token
NEXT_PUBLIC_POSTHOG_HOST=https://us.i.posthog.com

Get your PostHog project token from your PostHog project settings.

3. Run the Development Server
npm run dev
# or
pnpm dev

Open http://localhost:3000 with your browser to see the app.

Project Structure

src/
├── components/
│   └── Header.tsx           # Navigation header with auth state
├── contexts/
│   └── AuthContext.tsx      # Authentication context with PostHog integration
├── lib/
│   └── posthog-server.ts    # Server-side PostHog client
├── pages/
│   ├── _app.tsx             # App wrapper with Auth provider
│   ├── _document.tsx        # Document wrapper
│   ├── index.tsx            # Home/Login page
│   ├── burrito.tsx          # Demo feature page with event tracking
│   ├── profile.tsx          # User profile with error tracking demo
│   └── api/
│       └── auth/
│           └── login.ts     # Login API with server-side tracking
└── styles/
    └── globals.css          # Global styles

instrumentation-client.ts    # Client-side PostHog initialization

Key Integration Points

Client-side initialization (instrumentation-client.ts)
import posthog from "posthog-js"

posthog.init(process.env.NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN!, {
  api_host: "/ingest",
  ui_host: "https://us.posthog.com",
  defaults: '2026-01-30',
  capture_exceptions: true,
  debug: process.env.NODE_ENV === "development",
});
User identification (AuthContext.tsx)
posthog.identify(username, {
  username: username,
});
Event tracking (burrito.tsx)
posthog.capture('burrito_considered', {
  total_considerations: count,
  username: username,
});
Error tracking (profile.tsx)
posthog.captureException(error);
Server-side tracking (api/auth/login.ts)
const posthog = getPostHogClient();
posthog.capture({
  distinctId: username,
  event: 'server_login',
  properties: { ... }
});

Pages router differences from app router

This example uses Next.js Pages Router instead of App Router. Key differences:

  1. File-based routing: Pages in src/pages/ instead of src/app/

  2. _app.tsx: Custom App component wraps all pages

  3. API Routes: Located in src/pages/api/

  4. No 'use client': All pages are client-side by default

  5. useRouter: From next/router instead of next/navigation

  6. Head component: Using next/head for metadata instead of metadata export

Learn More

Deploy on Vercel

The easiest way to deploy your Next.js app is to use the Vercel Platform.

Check out the Next.js deployment documentation for more details.

instrumentation-client.ts

import posthog from "posthog-js"

posthog.init(process.env.NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN!, {
  api_host: "/ingest",
  ui_host: "https://us.posthog.com",
  // Include the defaults option as required by PostHog
  defaults: '2026-01-30',
  // Enables capturing unhandled exceptions via Error Tracking
  capture_exceptions: true,
  // Turn on debug in development mode
  debug: process.env.NODE_ENV === "development",
});

//IMPORTANT: Never combine this approach with other client-side PostHog initialization approaches, especially components like a PostHogProvider. instrumentation-client.ts is the correct solution for initializating client-side PostHog in Next.js 15.3+ apps.

next.config.ts

import type { NextConfig } from "next";

const nextConfig: NextConfig = {
  /* config options here */
  reactStrictMode: true,
  async rewrites() {
    return [
      {
        source: "/ingest/static/:path*",
        destination: "https://us-assets.i.posthog.com/static/:path*",
      },
      {
        source: "/ingest/:path*",
        destination: "https://us.i.posthog.com/:path*",
      },
    ];
  },
  // This is required to support PostHog trailing slash API requests
  skipTrailingSlashRedirect: true,
};

export default nextConfig;

src/components/Header.tsx

import Link from 'next/link';
import { useAuth } from '@/contexts/AuthContext';

export default function Header() {
  const { user, logout } = useAuth();

  return (
    <header className="header">
      <div className="header-container">
        <nav>
          <Link href="/">Home</Link>
          {user && (
            <>
              <Link href="/burrito">Burrito Consideration</Link>
              <Link href="/profile">Profile</Link>
            </>
          )}
        </nav>
        <div className="user-section">
          {user ? (
            <>
              <span>Welcome, {user.username}!</span>
              <button onClick={logout} className="btn-logout">
                Logout
              </button>
            </>
          ) : (
            <span>Not logged in</span>
          )}
        </div>
      </div>
    </header>
  );
}

src/contexts/AuthContext.tsx

import { createContext, useContext, useState, ReactNode } from 'react';
import posthog from 'posthog-js';

interface User {
  username: string;
  burritoConsiderations: number;
}

interface AuthContextType {
  user: User | null;
  login: (username: string, password: string) => Promise<boolean>;
  logout: () => void;
  incrementBurritoConsiderations: () => void;
}

const AuthContext = createContext<AuthContextType | undefined>(undefined);

const users: Map<string, User> = new Map();

export function AuthProvider({ children }: { children: ReactNode }) {
  // Use lazy initializer to read from localStorage only once on mount
  const [user, setUser] = useState<User | null>(() => {
    if (typeof window === 'undefined') return null;

    const storedUsername = localStorage.getItem('currentUser');
    if (storedUsername) {
      const existingUser = users.get(storedUsername);
      if (existingUser) {
        return existingUser;
      }
    }
    return null;
  });

  const login = async (username: string, password: string): Promise<boolean> => {
    try {
      const response = await fetch('/api/auth/login', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ username, password }),
      });

      if (response.ok) {
        const { user: userData } = await response.json();

        // Get or create user in local map
        let localUser = users.get(username);
        if (!localUser) {
          localUser = userData as User;
          users.set(username, localUser);
        }

        setUser(localUser);
        localStorage.setItem('currentUser', username);

        // Identify user in PostHog using username as distinct ID
        posthog.identify(username, {
          username: username,
        });

        // Capture login event
        posthog.capture('user_logged_in', {
          username: username,
        });

        return true;
      }
      return false;
    } catch (error) {
      console.error('Login error:', error);
      return false;
    }
  };

  const logout = () => {
    // Capture logout event before resetting
    posthog.capture('user_logged_out');
    posthog.reset();

    setUser(null);
    localStorage.removeItem('currentUser');
  };

  const incrementBurritoConsiderations = () => {
    if (user) {
      user.burritoConsiderations++;
      users.set(user.username, user);
      setUser({ ...user });
    }
  };

  return (
    <AuthContext.Provider value={{ user, login, logout, incrementBurritoConsiderations }}>
      {children}
    </AuthContext.Provider>
  );
}

export function useAuth() {
  const context = useContext(AuthContext);
  if (context === undefined) {
    throw new Error('useAuth must be used within an AuthProvider');
  }
  return context;
}

src/lib/posthog-server.ts

import { PostHog } from 'posthog-node';

let posthogClient: PostHog | null = null;

export function getPostHogClient() {
  if (!posthogClient) {
    posthogClient = new PostHog(
      process.env.NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN!,
      {
        host: process.env.NEXT_PUBLIC_POSTHOG_HOST,
        flushAt: 1,
        flushInterval: 0
      }
    );
  }
  return posthogClient;
}

export async function shutdownPostHog() {
  if (posthogClient) {
    await posthogClient.shutdown();
  }
}

src/pages/_app.tsx

import "@/styles/globals.css";
import type { AppProps } from "next/app";
import { AuthProvider } from "@/contexts/AuthContext";

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

src/pages/_document.tsx

import { Html, Head, Main, NextScript } from "next/document";

export default function Document() {
  return (
    <Html lang="en">
      <Head />
      <body>
        <Main />
        <NextScript />
      </body>
    </Html>
  );
}

src/pages/api/auth/login.ts

import type { NextApiRequest, NextApiResponse } from 'next';
import { getPostHogClient } from '@/lib/posthog-server';

const users = new Map<string, { username: string; burritoConsiderations: number }>();

export default async function handler(
  req: NextApiRequest,
  res: NextApiResponse
) {
  if (req.method !== 'POST') {
    return res.status(405).json({ error: 'Method not allowed' });
  }

  const { username, password } = req.body;

  if (!username || !password) {
    return res.status(400).json({ error: 'Username and password required' });
  }

  let user = users.get(username);
  const isNewUser = !user;

  if (!user) {
    user = { username, burritoConsiderations: 0 };
    users.set(username, user);
  }

  // Capture server-side login event
  const posthog = getPostHogClient();
  posthog.capture({
    distinctId: username,
    event: 'server_login',
    properties: {
      username: username,
      isNewUser: isNewUser,
      source: 'api'
    }
  });

  // Identify user on server side
  posthog.identify({
    distinctId: username,
    properties: {
      username: username,
      createdAt: isNewUser ? new Date().toISOString() : undefined
    }
  });

  return res.status(200).json({ success: true, user });
}

src/pages/api/hello.ts

// Next.js API route support: https://nextjs.org/docs/api-routes/introduction
import type { NextApiRequest, NextApiResponse } from "next";

type Data = {
  name: string;
};

export default function handler(
  req: NextApiRequest,
  res: NextApiResponse<Data>,
) {
  res.status(200).json({ name: "John Doe" });
}

src/pages/burrito.tsx

import { useState } from 'react';
import Head from 'next/head';
import { useRouter } from 'next/router';
import posthog from 'posthog-js';
import { useAuth } from '@/contexts/AuthContext';
import Header from '@/components/Header';

export default function BurritoPage() {
  const { user, incrementBurritoConsiderations } = useAuth();
  const router = useRouter();
  const [hasConsidered, setHasConsidered] = useState(false);

  // Redirect to home if not logged in
  if (!user) {
    router.push('/');
    return null;
  }

  const handleConsideration = () => {
    incrementBurritoConsiderations();
    setHasConsidered(true);
    setTimeout(() => setHasConsidered(false), 2000);

    // Capture burrito consideration event
    posthog.capture('burrito_considered', {
      total_considerations: user.burritoConsiderations + 1,
      username: user.username,
    });
  };

  return (
    <>
      <Head>
        <title>Burrito Consideration - Burrito Consideration App</title>
        <meta name="description" content="Consider the potential of burritos" />
        <meta name="viewport" content="width=device-width, initial-scale=1" />
        <link rel="icon" href="/favicon.ico" />
      </Head>
      <Header />
      <main>
        <div className="container">
          <h1>Burrito consideration zone</h1>
          <p>Take a moment to truly consider the potential of burritos.</p>

          <div style={{ textAlign: 'center' }}>
            <button
              onClick={handleConsideration}
              className="btn-burrito"
            >
              I have considered the burrito potential
            </button>

            {hasConsidered && (
              <p className="success">
                Thank you for your consideration! Count: {user.burritoConsiderations}
              </p>
            )}
          </div>

          <div className="stats">
            <h3>Consideration stats</h3>
            <p>Total considerations: {user.burritoConsiderations}</p>
          </div>
        </div>
      </main>
    </>
  );
}

src/pages/index.tsx

import { useState } from 'react';
import Head from 'next/head';
import { useAuth } from '@/contexts/AuthContext';
import Header from '@/components/Header';

export default function Home() {
  const { user, login } = useAuth();
  const [username, setUsername] = useState('');
  const [password, setPassword] = useState('');
  const [error, setError] = useState('');

  const handleSubmit = async (e: React.FormEvent) => {
    e.preventDefault();
    setError('');

    try {
      const success = await login(username, password);
      if (success) {
        setUsername('');
        setPassword('');
      } else {
        setError('Please provide both username and password');
      }
    } catch (err) {
      console.error('Login failed:', err);
      setError('An error occurred during login');
    }
  };

  return (
    <>
      <Head>
        <title>Burrito Consideration App</title>
        <meta name="description" content="Consider the potential of burritos" />
        <meta name="viewport" content="width=device-width, initial-scale=1" />
        <link rel="icon" href="/favicon.ico" />
      </Head>
      <Header />
      <main>
        {user ? (
          <div className="container">
            <h1>Welcome back, {user.username}!</h1>
            <p>You are now logged in. Feel free to explore:</p>
            <ul>
              <li>Consider the potential of burritos</li>
              <li>View your profile and statistics</li>
            </ul>
          </div>
        ) : (
          <div className="container">
            <h1>Welcome to Burrito Consideration App</h1>
            <p>Please sign in to begin your burrito journey</p>

            <form onSubmit={handleSubmit} className="form">
              <div className="form-group">
                <label htmlFor="username">Username:</label>
                <input
                  type="text"
                  id="username"
                  value={username}
                  onChange={(e) => setUsername(e.target.value)}
                  placeholder="Enter any username"
                />
              </div>

              <div className="form-group">
                <label htmlFor="password">Password:</label>
                <input
                  type="password"
                  id="password"
                  value={password}
                  onChange={(e) => setPassword(e.target.value)}
                  placeholder="Enter any password"
                />
              </div>

              {error && <p className="error">{error}</p>}

              <button type="submit" className="btn-primary">Sign In</button>
            </form>

            <p className="note">
              Note: This is a demo app. Use any username and password to sign in.
            </p>
          </div>
        )}
      </main>
    </>
  );
}

src/pages/profile.tsx

import Head from 'next/head';
import { useRouter } from 'next/router';
import posthog from 'posthog-js';
import { useAuth } from '@/contexts/AuthContext';
import Header from '@/components/Header';

export default function ProfilePage() {
  const { user } = useAuth();
  const router = useRouter();

  // Redirect to home if not logged in
  if (!user) {
    router.push('/');
    return null;
  }

  const triggerTestError = () => {
    try {
      throw new Error('Test error for PostHog error tracking');
    } catch (err) {
      posthog.captureException(err);
      console.error('Captured error:', err);
      alert('Error captured and sent to PostHog!');
    }
  };

  return (
    <>
      <Head>
        <title>Profile - Burrito Consideration App</title>
        <meta name="description" content="Your burrito consideration profile" />
        <meta name="viewport" content="width=device-width, initial-scale=1" />
        <link rel="icon" href="/favicon.ico" />
      </Head>
      <Header />
      <main>
        <div className="container">
          <h1>User Profile</h1>

          <div className="stats">
            <h2>Your Information</h2>
            <p><strong>Username:</strong> {user.username}</p>
            <p><strong>Burrito Considerations:</strong> {user.burritoConsiderations}</p>
          </div>

          <div style={{ marginTop: '2rem' }}>
            <button onClick={triggerTestError} className="btn-primary" style={{ backgroundColor: '#dc3545' }}>
              Trigger Test Error (for PostHog)
            </button>
          </div>

          <div style={{ marginTop: '2rem' }}>
            <h3>Your Burrito Journey</h3>
            {user.burritoConsiderations === 0 ? (
              <p>You haven&apos;t considered any burritos yet. Visit the Burrito Consideration page to start!</p>
            ) : user.burritoConsiderations === 1 ? (
              <p>You&apos;ve considered the burrito potential once. Keep going!</p>
            ) : user.burritoConsiderations < 5 ? (
              <p>You&apos;re getting the hang of burrito consideration!</p>
            ) : user.burritoConsiderations < 10 ? (
              <p>You&apos;re becoming a burrito consideration expert!</p>
            ) : (
              <p>You are a true burrito consideration master! 🌯</p>
            )}
          </div>
        </div>
      </main>
    </>
  );
}

Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Security

No issues found by our static scan· No issues found

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Attribution and licence

Created by
PostHog
Publisher
PostHog (Official)
Source
PostHog/skills · skills/posthog/integration/skills/nextjs-pages-router · commit a5d30e7
Licence
MIT License (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • ATTRIBUTION.md (written by AutoGineer)
Synced
Also distributed in
PostHog/skills

AutoGineer is not affiliated with or endorsed by PostHog or PostHog.

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