Astro

PostHog makes it easy to get data about traffic and usage of your Astro 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 Astro app using the JavaScript Web SDK.

Beta: integration via LLM

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

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

Installation

In your src/components folder, create a posthog.astro file:

cd ./src/components
# or 'cd ./src && mkdir components && cd ./components' if your components folder doesnt exist
touch posthog.astro

In this file, add your Web snippet which you can find in your project settings. Be sure to include the is:inline directive to prevent Astro from processing it, or you will get Typescript and build errors that property 'posthog' does not exist on type 'Window & typeof globalThis'.

---
// src/components/posthog.astro
---
<script is:inline>
  !function(t,e){var o,n,p,r;e.__SV||(window.posthog=e,e._i=[],e.init=function(i,s,a){function g(t,e){var o=e.split(".");2==o.length&&(t=t[o[0]],e=o[1]),t[e]=function(){t.push([e].concat(Array.prototype.slice.call(arguments,0)))}}(p=t.createElement("script")).type="text/javascript",p.crossOrigin="anonymous",p.async=!0,p.src=s.api_host+"/static/array.js",(r=t.getElementsByTagName("script")[0]).parentNode.insertBefore(p,r);var u=e;for(void 0!==a?u=e[a]=[]:a="posthog",u.people=u.people||[],u.toString=function(t){var e="posthog";return"posthog"!==a&&(e+="."+a),t||(e+=" (stub)"),e},u.people.toString=function(){return u.toString(1)+".people (stub)"},o="capture identify alias people.set people.set_once set_config register register_once unregister opt_out_capturing has_opted_out_capturing opt_in_capturing reset isFeatureEnabled onFeatureFlags getFeatureFlag getFeatureFlagResult reloadFeatureFlags group updateEarlyAccessFeatureEnrollment getEarlyAccessFeatures getActiveMatchingSurveys getSurveys getNextSurveyStep onSessionId".split(" "),n=0;n<o.length;n++)g(u,o[n]);e._i.push([i,s,a])},e.__SV=1)}(document,window.posthog||[]);
  posthog.init('<ph_project_token>', {
    api_host:'https://us.i.posthog.com',
    defaults: '2026-05-30'
  })
</script>

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.

---
// src/components/posthog.astro
---
<script is:inline>
  if (!window.__posthog_initialized) {
    window.__posthog_initialized = true;

    !function(t,e){var o,n,p,r;e.__SV||(window.posthog=e,e._i=[],e.init=function(i,s,a){function g(t,e){var o=e.split(".");2==o.length&&(t=t[o[0]],e=o[1]),t[e]=function(){t.push([e].concat(Array.prototype.slice.call(arguments,0)))}}(p=t.createElement("script")).type="text/javascript",p.crossOrigin="anonymous",p.async=!0,p.src=s.api_host+"/static/array.js",(r=t.getElementsByTagName("script")[0]).parentNode.insertBefore(p,r);var u=e;for(void 0!==a?u=e[a]=[]:a="posthog",u.people=u.people||[],u.toString=function(t){var e="posthog";return"posthog"!==a&&(e+="."+a),t||(e+=" (stub)"),e},u.people.toString=function(){return u.toString(1)+".people (stub)"},o="capture identify alias people.set people.set_once set_config register register_once unregister opt_out_capturing has_opted_out_capturing opt_in_capturing reset isFeatureEnabled onFeatureFlags getFeatureFlag getFeatureFlagResult reloadFeatureFlags group updateEarlyAccessFeatureEnrollment getEarlyAccessFeatures getActiveMatchingSurveys getSurveys getNextSurveyStep onSessionId".split(" "),n=0;n<o.length;n++)g(u,o[n]);e._i.push([i,s,a])},e.__SV=1)}(document,window.posthog||[]);

    posthog.init('<ph_project_token>', {
      api_host: 'https://us.i.posthog.com',
      defaults: '2026-05-30',
      capture_pageview: 'history_change'
    })
  }
</script>

The next step is to a create a Layout where we will use posthog.astro. Create a new file PostHogLayout.astro in your src/layouts folder:

cd .. && cd .. # move back to your base directory if you're still in src/components/posthog.astro
cd ./src/layouts
# or 'cd ./src && mkdir layouts && cd ./layouts' if your layouts folder doesn't exist yet
touch PostHogLayout.astro

Add the following code to PostHogLayout.astro:

---
import PostHog from '../components/posthog.astro'
---
<head>
    <PostHog />
</head>

Lastly, update index.astro to wrap your existing app components with the new Layout:

---
import PostHogLayout from '../layouts/PostHogLayout.astro';
---
<PostHogLayout>
  <!-- your existing app components -->
</PostHogLayout>

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.

If your app calls your own backend, tracing_headers adds X-POSTHOG-DISTINCT-ID and X-POSTHOG-SESSION-ID to matching fetch and XMLHttpRequest requests. This lets server-side SDKs link backend events, errors, and LLM traces back to frontend sessions and replays. Use hostnames only, without protocols or paths.

posthog.init('<ph_project_token>', {
  api_host: 'https://us.i.posthog.com',
  // Optional: send PostHog session/user context to your backend
  tracing_headers: ['api.example.com'],
})

This works in local development too, but match on the hostname alone: use 'localhost', not 'localhost:3000'. Ports are never part of a hostname, so a value with one in it never matches anything. localhost and 127.0.0.1 are also different hostnames — use whichever your app actually calls.

Tracing headers help you attribute events across front and backend consistently. When this isn't available, use your server-side stable IDs to deduce the matching distinctId, and pass it in when capturing the event.

Next steps

For any technical questions for how to integrate specific PostHog features into Astro (such as analytics, feature flags, A/B testing, surveys, etc.), have a look at our JavaScript Web SDK docs.

Alternatively, the following tutorials can help you get started:

• How to set up Astro analytics, feature flags, and more
• How to set up A/B tests in Astro
• How to set up surveys in Astro