n8n Workflow: Deduplicate Server-Side Meta CAPI Conversions

Deduplicate Meta Conversions API events before they hit Facebook—using n8n

This n8n workflow receives server-side Meta CAPI conversion events via a webhook, normalizes and hashes supported identifiers, deduplicates retries with an n8n Data Table, and then submits the validated event to the Meta Conversions API (Graph API) to confirm Meta accepted it.

What this workflow does

• Receives conversion events: Listens for POST webhook requests containing a conversion event in plain JSON.
• Normalizes fields and time: Normalizes event fields (including event time) and repairs the fbc value from a raw fbclid when needed.
• Deduplicates retries: Checks an n8n Data Table for an existing dedupe key and stops duplicates before they reach Meta.
• Hashes supported identifiers: Records the event’s dedupe key in the Data Table and applies SHA-256 hashing to user identifiers such as email, phone, name, city, zip, and country.
• Builds the Meta payload: Creates a Meta Conversions API payload including event_id, required action/source fields, and unhashed external_id, plus an optional test_event_code.
• Validates Meta response: Sends the event to the Meta Graph API endpoint for your pixel/dataset and verifies events_received in the response body.

Use cases

• Prevent double-counting when your backend or CRM retries webhook deliveries.
• Ensure consistent Meta CAPI event submission for SaaS signup, purchase, or lead conversions with reliable deduplication.
• Improve server-side conversion accuracy by standardizing timestamps and repairing fbc from fbclid.

Technical details

• n8n Webhook (incoming conversion JSON)
• n8n Data Table (dedupe storage via dedupe_key)
• Code + Crypto (field normalization and SHA-256 hashing)
• Set (payload assembly)
• HTTP request to Meta Graph API using an HTTP Query Auth credential named access_token
• Nodes/inputs referenced: set, code, crypto, webhook, data table, sticky note

Setup

• Create a Data Table with a dedupe_key text column and set its name in the workflow Settings.
• Provide your Meta pixel/dataset ID and Graph API version in Settings.
• Add your Meta access token as an HTTP Query Auth credential named access_token and attach it to the Meta HTTP request.
• Copy the webhook production URL and configure your CRM, backend, or form provider to POST conversion events to it.