Astro experiments installation

Create the PostHog component

Required

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

Terminal
cd ./src/components
# or 'cd ./src && mkdir components && cd ./components' if your components folder doesn't exist
touch posthog.astro

In this file, add your PostHog web snippet. Be sure to include the is:inline directive to prevent Astro from processing it:

src/components/posthog.astro
---
// 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.async=!0,p.src=s.api_host.replace(".i.posthog.com","-assets.i.posthog.com")+"/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="init capture register register_once register_for_session unregister opt_out_capturing has_opted_out_capturing opt_in_capturing reset isFeatureEnabled getFeatureFlag getFeatureFlagPayload reloadFeatureFlags group identify setPersonProperties setPersonPropertiesForFlags resetPersonPropertiesForFlags setGroupPropertiesForFlags resetGroupPropertiesForFlags resetGroups onFeatureFlags addFeatureFlagsHandler onSessionId getSurveys getActiveMatchingSurveys renderSurvey canRenderSurvey getNextSurveyStep".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_api_key>', {
        api_host: 'https://us.i.posthog.com',
        defaults: '2025-11-30'
    })
</script>

Create a layout

Required

Create a layout where we will use posthog.astro. Create a new file PostHogLayout.astro in your src/layouts folder:

Terminal
cd ./src/layouts
# or 'cd ./src && mkdir layouts && cd ./layouts' if your layouts folder doesn't exist
touch PostHogLayout.astro

Add the following code to PostHogLayout.astro:

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

Use the layout in your pages

Required

Update your pages (like index.astro) to wrap your app with the new layout:

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

Implement your experiment

Required

Experiments run on top of our feature flags. You can define which version of your code runs based on the return value of the feature flag:

if (posthog.getFeatureFlag('your-experiment-feature-flag') === 'test') {
    // Do something differently for this user
} else {
    // It's a good idea to let control variant always be the default behaviour,
    // so if something goes wrong with flag evaluation, you don't break your app.
}

// Test that it works
posthog.featureFlags.overrideFeatureFlags({ flags: {'your-experiment-feature-flag': 'test'} })

5
Run your experiment
Required
Once you've implemented the feature flag in your code, you'll enable it for a target audience by creating a new experiment in the PostHog dashboard.

Next steps

Recommended

Resource	Description
Creating an experiment	How to create an experiment in PostHog
Adding experiment code	How to implement experiments for all platforms
Statistical significance	Understanding when results are meaningful
Experiment insights	How to analyze your experiment data
More tutorials	Other real-world examples and use cases

Astro experiments installation

Create the PostHog component

Create a layout

Use the layout in your pages

Implement your experiment

Run your experiment

Next steps

Community questions

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