PostHog

→ PostHog Documentation

Requirements: A server runtime. The /ingest proxy relies on Next.js rewrites, so PostHog is unavailable with the cloudflare-static deployment.

What create-faster adds

Files added:

src/
└── instrumentation-client.ts   # posthog.init through the /ingest proxy

Modified files:

• next.config.ts - Adds the /ingest rewrites and skipTrailingSlashRedirect
• src/proxy.ts - Excludes /ingest from the matcher

Environment variables:

• NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN - PostHog project token (scoped to app). PostHog is not initialized when it is unset.

instrumentation-client.ts

Runs once on the client before hydration (Next.js 15.3+ convention):

import posthog from 'posthog-js';

if (process.env.NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN) {
  posthog.init(process.env.NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN, {
    api_host: '/ingest',
    ui_host: 'https://us.posthog.com',
    defaults: '2026-05-30',
    capture_exceptions: true,
    debug: process.env.NODE_ENV === 'development',
  });
}

next.config.ts

Events are sent to your own domain and proxied to PostHog Cloud (US), which keeps requests same-origin and avoids ad-blockers:

async rewrites() {
  return [
    {
      source: '/ingest/static/:path*',
      destination: 'https://us-assets.i.posthog.com/static/:path*',
    },
    {
      source: '/ingest/array/:path*',
      destination: 'https://us-assets.i.posthog.com/array/:path*',
    },
    {
      source: '/ingest/:path*',
      destination: 'https://us.i.posthog.com/:path*',
    },
  ];
},
skipTrailingSlashRedirect: true,

skipTrailingSlashRedirect is required: PostHog endpoints such as /e/ end with a slash, and Next.js would otherwise redirect them and drop events. For PostHog Cloud EU, replace us with eu in the destinations and ui_host.

Turborepo mode: Files are scoped to the app that selects PostHog (apps/{appName}/), and the env var lands in that app's .env.example.