PostHog

Koryla sends experiment assignments to PostHog as $experiment_started events — the same event format PostHog's own feature flags use, so they integrate cleanly with the Experiments and Insights features.

Setup

1. In your PostHog project, go to Project Settings → Project API key and copy the key (starts with phc_).
2. If you're on PostHog Cloud EU, also note your host: https://eu.i.posthog.com. US Cloud uses https://us.i.posthog.com.
3. Enter the API key (and host if needed) in Dashboard → Integrations → PostHog and toggle it on.

What gets sent

{
  "event": "$experiment_started",
  "distinct_id": "[session_id]",
  "properties": {
    "experiment_name": "Homepage CTA Test",
    "variant": "Blue button",
    "$experiment_id": "a1b2c3...",
    "$variant_id": "x9y8z7..."
  }
}

The distinct_id is the Koryla session ID — an anonymous identifier persisted in the ky_session cookie.

Analyzing results in PostHog

Option 1 — Experiments

If you use PostHog's Experiments feature, Koryla events will appear in the experiment results automatically when the experiment_name matches.

Option 2 — Funnel in Insights

1. Create a new Insight → Funnel
2. Step 1: Filter by $experiment_started where experiment_name = "Your Test"
3. Step 2: Add your goal event (e.g. purchase, signed_up)
4. Break down by variant

This shows conversion rates per variant over any date range.

Notes

• Events fire once per visitor per experiment (on new ky_ cookie assignment).
• The distinct_id is anonymous — if you also have PostHog's JS snippet on your pages and users are identified, the events won't be automatically merged. For full funnel attribution, pass your own user ID via a custom webhook integration instead.