Webflow experiments installation

  1. Copy the web snippet

    Required

    First, copy your PostHog web snippet:

    HTML
    <script>
        !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_token>', {
            api_host: 'https://us.i.posthog.com',
            defaults: '2026-01-30'
        })
    </script>

  2. Add to Webflow

    Required

    Go to your Webflow site settings by clicking on the menu icon in the top left. If you haven't already, sign up for at least the Basic site plan. This enables you to add custom code. Then:

    1. Go to the Custom code tab in site settings.
    2. In the Head code section, paste your PostHog snippet and press save.
    3. Publish your site.

  3. 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'} })

  4. 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.

  5. Next steps

    Recommended

    Now that you're running experiments, continue with the resources below to learn what else Experiments enables within the PostHog platform.

    ResourceDescription
    Creating an experimentHow to create an experiment in PostHog
    Adding experiment codeHow to implement experiments for all platforms
    Statistical significanceUnderstanding when results are meaningful
    Experiment insightsHow to analyze your experiment data
    More tutorialsOther real-world examples and use cases

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