Gatsby

This library was built by the community. Thanks to Ritesh Kadmawala for building it.

Gatsby behaves like a single-page app which means to track $pageview events special care is needed. This integration takes care of that.

Install

yarn add gatsby-plugin-posthog

or

npm install --save gatsby-plugin-posthog

If your site sets a Content-Security-Policy, it needs to allow PostHog. This applies to the snippet and to package installs alike: the SDK lazy-loads extra bundles (session replay, surveys) from PostHog's CDN, and sends events to the ingestion host. PostHog serves from subdomains of posthog.com that change over time, so allow the wildcard:

PostHog AI

script-src 'self' https://*.posthog.com;
connect-src 'self' https://*.posthog.com;
worker-src 'self' blob: data:;

script-src covers the snippet and the lazy-loaded bundles, connect-src covers event ingestion and feature flags, and worker-src covers session replay. The toolbar needs a few more, or use a reverse proxy so everything is first-party. Failing to do so causes silent failures where capture and identify calls never send, so the integration looks complete while zero events arrive. Remember connect-src falls back to default-src, so default-src 'self' blocks event delivery even when the script itself is bundled.

How to use

// In your gatsby-config.js
module.exports = {
  plugins: [
    {
      resolve: `gatsby-plugin-posthog`,
      options: {
        // Specify the API key for your PostHog Project (required)
        apiKey: "<ph_project_token>",
        // Specify the app host if self-hosting (optional, default: https://us.i.posthog.com)
        apiHost: "https://us.i.posthog.com",
        // Puts tracking script in the head instead of the body (optional, default: true)
        head: true,
        // Enable posthog analytics tracking during development (optional, default: false)
        isEnabledDevMode: true
      },
    },
  ],
}

This will automatically start tracking pageviews, clicks and more.

In your code you can access posthog via window.posthog.

For more instructions, see browser JS library.

Identifying users

Identifying users is required. Call posthog.identify('your-user-id') after login to link events to a known user. This is what connects frontend event captures, session replays, LLM traces, and error tracking to the same person — and lets backend events link back too.

Use a stable ID from your auth system when possible, not an email or display name. Send those as person properties instead. If your app has no other stable key, email works as a fallback if they are unique. Never a shared literal like "anonymous" or "user", which pools many people onto one person and corrupts their data. When no ID is available at all, skip the identify and retain the anonymous distinct ID that's automatically assigned.

Call posthog.reset() on logout, so the next person to use the browser doesn't inherit the last one's identity.

See our guide on identifying users for how to set this up.