Substack and Beehiiv don't speak CAPI
When a paid subscriber upgrades, your newsletter platform fires an internal hook. It does not POST to Meta Conversions API, Google Ads, or Klaviyo. Your ad reports show the click — never the upgrade.
TRACKLAYER · CREATORS
Attribution for the post-Substack creator stack.
Klaviyo, Stripe Billing, Beehiiv, Kajabi, and Memberstack subscribers fan out to Meta, Google, and Klaviyo as durable, signed, server-side events — with subscriber LTV, retention insights, anomaly auto-pause, and audit chain integrity preserved end-to-end.
subscriber.createdBeehiivcaptured
subscriber.paidBeehiiv$10/mo
paid_subscriberTrackLayertranslated
SubscribeMeta CAPIdelivered
subscribe_paidGoogle Adsdelivered
started_paid_subscriptionKlaviyoflow triggered
CREATOR SIGNAL PIPELINE
§ 01 · WHY CREATOR ATTRIBUTION IS BROKEN
Your newsletter platform doesn't talk to your ad platform.
Stripe shows the dollars but not the publication. Meta sees the click but not the upgrade. The signal gap is structural, not skill — and creator-platform vendors have not closed it.
Stripe-only attribution misses creator stack
Stripe sees the payment, not the publication, the post, or the tier. Lifetime value lives inside Beehiiv or Kajabi. Optimizing campaigns on raw Stripe Subscribe events flattens that signal.
iOS opens kill open-rate signal
Mail Privacy Protection auto-opens email — engagement signal evaporates. Server-side post.clicked from Beehiiv is the only reliable engagement event, but it never reaches Meta.
// 02 · HOW THE PIPELINE WORKS
Four steps from creator-platform webhook to ad-platform conversion.
STEP 01
Provider webhook
Beehiiv (native) or Substack-via-Zapier or Kajabi or Memberstack POSTs subscriber lifecycle events to TrackLayer with HMAC signature.
STEP 02
Translate to canonical event
TrackLayer maps subscriber.created → subscriber_signup, subscriber.paid → paid_subscriber, post.clicked → content_engaged. One taxonomy across providers.
STEP 03
Enrich with revenue + identity
Currency, tier, plan name, publication ID flow through. Email is hashed for CAPI. Provider event ID powers cross-stack deduplication.
STEP 04
Fan out to ad + lifecycle stack
Meta CAPI as Subscribe / CompleteRegistration. Google Ads as subscribe_paid for tROAS. Klaviyo as started_paid_subscription to trigger nurture flows.
03 · VS STRIPE + SEGMENT + PIRSCH
What changes when the creator platform owns the webhook.
§ 04 · IN PRODUCTION
Three creator stacks running TrackLayer today.
Names redacted at the operator's request — figures verified against TrackLayer event logs.
northfield-newsletter.com
Paid Substack newsletter, $7,800 MRR
- $2,400/mo on Meta retargeting for paid upgrades
- Before TrackLayer: zero subscriber.paid events visible to Meta
- After TrackLayer: 41 paid upgrades attributed in week 3 — Meta CPA cut from $96 to $58
halcyon-podcast.io
Kajabi members, $14,200 MRR, podcast + course bundles
- $1,800/mo Google Ads + $900/mo TikTok ads
- Course completion + offer.purchased flow into both ad stacks
- Klaviyo segments off content_engaged drive 22% renewal lift on month-3 cohorts
glasshouse-courses.co
Memberstack-powered Webflow site, $4,400 MRR
- Meta Advantage+ campaigns optimized on plan.purchased
- member.canceled → 14-day Klaviyo win-back automation
- Bookable plan-purchase value to Google Ads — first month ROAS hit 3.4x
05 · PRICING
Built for solo operators. Lite tier covers the full stack.
Creator integrations work from $19/mo Lite. No enterprise lock-up. No per-event surcharge for newsletter signups.
LITE
$19/mo
Beehiiv + Memberstack + Substack. Up to 25k events/mo.
GROWTH
$79/mo
Adds Kajabi, Klaviyo nurture, content_engaged retargeting.
BUSINESS
$199/mo
Multi-publication, Stripe link, custom audience exports.
// 06 · IMPLEMENTATION REFERENCE
Wire Beehiiv → Meta CAPI in five minutes.
Step-by-step recipe with sample webhook payload and the canonical TrackLayer event it produces.
RECIPE
Beehiiv → Meta CAPI in 5 minutes
- Open Beehiiv → Settings → Webhooks → New webhook.
- Paste your TrackLayer URL with merchant_id query.
- Select subscriber.created, subscriber.paid, post.clicked.
- Copy the HMAC secret into TrackLayer settings.
- Connect Meta CAPI in TrackLayer — events flow immediately.
POST /v1/integrations/beehiiv/webhook?merchant_id=mer_5f3a
X-Beehiiv-Signature: sha256=2b8f...
{
"event": "subscriber.paid",
"event_id": "evt_01HF8AKZ",
"occurred_at": 1761500000,
"data": {
"id": "sub_8b2x",
"email": "reader@halcyon.io",
"publication_id": "pub_north",
"tier": "premium",
"amount_cents": 1000,
"currency": "USD"
}
}
→ canonical: paid_subscriber
→ Meta CAPI: Subscribe ($10.00 USD)
→ Klaviyo: started_paid_subscription§ 07 · FAQ
Implementation questions.
Does Substack actually support webhooks?
Not natively. Substack provides email forwards and an admin export. Creators wire Substack → Zapier → TrackLayer using a per-merchant shared secret. The Zap runs on `paid subscriber added`, `subscription_canceled`, and `subscriber added` triggers and POSTs the canonical Zapier shape to /v1/integrations/substack/webhook.
What plan does this run on?
Creator integrations are available from Lite ($19/mo) up. Solo newsletter operators with a few thousand subscribers can wire the full Beehiiv → Meta + Google + Klaviyo stack without paying enterprise pricing.
How does the platform know which Substack/Beehiiv account is mine?
Every webhook URL carries `?merchant_id=<your-id>` and a per-provider HMAC secret stored on the merchants table. The signature is verified before any payload is processed — providers without a valid signature get a 401 and never reach the ingestion pipeline.
What happens if a webhook fires twice?
Each webhook carries a provider-supplied event_id. TrackLayer caches that in IDENTITY_KV for 30 days and skips duplicates. Beehiiv retries, Memberstack retries, and Zap re-runs all dedupe automatically.
08 · BUILT FOR CREATORS
Subscriber LTV + retention insights.
Track subscriber lifetime value by cohort, surface retention trends before churn accelerates, and maintain full audit chain integrity across every platform.
09 · NEXT STEP
Wire your creator stack into TrackLayer.
Free 14-day trial. Solo-operator pricing from $19/mo. Native Beehiiv + Memberstack signatures, Substack-via-Zapier, Kajabi bearer-token authentication — all live.