Posthog: Product Analytics That Don't Require a Data Team

Mixpanel and Amplitude cost thousands per month at scale. PostHog is open-source, self-hostable, and free up to 1M events/month. It gives you funnels, session replay, feature flags, and A/B testing in one tool.

Install

npm install posthog-js posthog-node

Client Setup (Next.js)

// providers/PosthogProvider.tsx
'use client';
import posthog from 'posthog-js';
import { PostHogProvider } from 'posthog-js/react';
import { useEffect } from 'react';

export function PHProvider({ children }: { children: React.ReactNode }) {
  useEffect(() => {
    posthog.init(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
      api_host: process.env.NEXT_PUBLIC_POSTHOG_HOST ?? 'https://us.i.posthog.com',
      capture_pageview: false, // We'll do this manually
    });
  }, []);

  return <PostHogProvider client={posthog}>{children}</PostHogProvider>;
}

Tracking Events

import { usePostHog } from 'posthog-js/react';

function CheckoutButton({ plan }) {
  const posthog = usePostHog();

  return (
    <button onClick={() => {
      posthog.capture('checkout_started', {
        plan,
        price: PRICES[plan],
        source: 'pricing_page',
      });
      router.push('/checkout');
    }}>
      Get Started
    </button>
  );
}

Identifying Users

// After login
posthog.identify(user.id, {
  email: user.email,
  name: user.name,
  plan: user.plan,
  createdAt: user.createdAt,
});

// After logout
posthog.reset();

Server-Side Events

// posthog.server.ts
import { PostHog } from 'posthog-node';

const posthog = new PostHog(process.env.POSTHOG_KEY!, {
  host: 'https://us.i.posthog.com',
  flushAt: 20,
  flushInterval: 10000,
});

// In Stripe webhook handler
posthog.capture({
  distinctId: user.id,
  event: 'subscription_started',
  properties: { plan: 'pro', amount: 2900 },
});

await posthog.shutdown(); // Flush before serverless function exits

Feature Flags

// Server-side flag check
const isEnabled = await posthog.isFeatureEnabled('new-dashboard', userId);

// Client-side
const { isFeatureEnabled } = usePostHog();
const showNewUI = isFeatureEnabled('new-dashboard');

Key Events to Track for SaaS

Event	When
signup_completed	User finishes onboarding
feature_used	Core feature activated
checkout_started	Clicked pricing CTA
subscription_started	Payment confirmed
subscription_cancelled	Churn event
invite_sent	Viral loop action

PostHog ships pre-configured in the AI SaaS Starter Kit — client + server setup, key SaaS events pre-wired. $99 at whoffagents.com.