Cross-Platform Retargeting Sync

Prerequisites

• Meta Business Manager with Marketing API access and valid access token
• LinkedIn Campaign Manager with Marketing API access and OAuth 2.0 token
• Google Ads account with API access and developer token
• n8n instance for orchestrating syncs
• Attio CRM with customer records (for exclusion lists)

Steps

1. Export customer exclusion list from CRM

Query Attio for all current customers and recently converted leads. These must be excluded from retargeting on every platform.

GET https://api.attio.com/v2/lists/{customer-list-id}/entries
Headers: Authorization: Bearer {attio-api-key}

Extract email addresses. Hash each with SHA-256 for privacy compliance before uploading to ad platforms.

2. Upload exclusion audience to Meta

POST https://graph.facebook.com/v18.0/act_{ad-account-id}/customaudiences
{
  "name": "Exclusion - Current Customers",
  "subtype": "CUSTOM",
  "customer_file_source": "USER_PROVIDED_ONLY"
}

Then upload hashed emails:

POST https://graph.facebook.com/v18.0/{audience-id}/users
{
  "payload": {
    "schema": ["EMAIL_SHA256"],
    "data": [["<sha256-hash-1>"], ["<sha256-hash-2>"]]
  }
}

3. Upload exclusion audience to LinkedIn

POST https://api.linkedin.com/v2/dmpSegments
{
  "name": "Exclusion - Current Customers",
  "type": "USER",
  "sourcePlatform": "FIRST_PARTY"
}

Upload hashed emails via the DMP Segment entity upload endpoint. LinkedIn requires SHA-256 hashed emails.

4. Upload exclusion audience to Google Ads

Use the Google Ads API UserListService:

POST /customers/{customer-id}/userLists:mutate
{
  "operations": [{
    "create": {
      "name": "Exclusion - Current Customers",
      "crmBasedUserList": {
        "uploadKeyType": "CRM_ID",
        "dataSourceType": "FIRST_PARTY"
      },
      "membershipLifeSpan": 30
    }
  }]
}

Then upload via OfflineUserDataJobService with SHA-256 hashed emails.

5. Sync website visitor segments across platforms

Each platform has its own pixel/tag for building visitor audiences. Ensure consistent segment definitions:

| Segment | Meta Rule | LinkedIn Rule | Google Rule | |---------|-----------|---------------|-------------| | High intent (pricing/demo page, 14d) | url contains /pricing OR /demo, retention_days: 14 | Insight Tag + URL rule /pricing OR /demo, lookback 14d | Google Ads tag + URL rule, membership 14d | | Medium intent (2+ pages, 30d) | event: PageView, count >= 2, retention_days: 30 | Insight Tag + page count rule, lookback 30d | Google Analytics audience: sessions >= 2, 30d | | Low intent (homepage bounce, 7d) | url = homepage, retention_days: 7 | Insight Tag + URL rule, lookback 7d | Google Ads tag, homepage only, 7d |

Verify audience sizes via each platform's API after 48 hours of pixel data collection.

6. Sync conversion events for optimization

Report conversions back to each platform so their algorithms optimize toward the right outcomes:

Meta CAPI:

POST https://graph.facebook.com/v18.0/{pixel-id}/events
{
  "data": [{
    "event_name": "Lead",
    "event_time": {unix-timestamp},
    "user_data": {"em": ["{sha256-email}"]},
    "event_source_url": "{landing-page-url}",
    "event_id": "{unique-id}"
  }]
}

LinkedIn Conversions API:

POST https://api.linkedin.com/rest/conversionEvents
{
  "conversion": "{conversion-urn}",
  "conversionHappenedAt": {epoch-ms},
  "user": {"userIds": [{"idType": "SHA256_EMAIL", "idValue": "{hash}"}]}
}

Google Ads offline conversions:

POST /customers/{id}/offlineUserDataJobs:create

Upload click ID + conversion data pairs via OfflineUserDataJobService.

7. Schedule automated sync via n8n

Build an n8n workflow triggered by a daily cron at 02:00 UTC:

1. Pull new customers and conversions from Attio (last 24h)
2. Hash emails with SHA-256
3. Upload to Meta, LinkedIn, and Google exclusion audiences in parallel
4. Push conversion events to all three CAPI/offline endpoints
5. Log sync results to PostHog: retargeting_audience_sync event with properties {platform, records_synced, errors}

Error handling

• If any platform API returns 429 (rate limit): retry with exponential backoff (2s, 4s, 8s, max 3 retries)
• If audience upload fails: log error to PostHog, send Slack alert, do not block other platform syncs
• If audience size drops below 100 on any platform: alert — audiences below 100 cannot be targeted