Matomo Cross-Domain Tracking

Overview

Cross-domain tracking in Matomo ensures visitor sessions persist when users navigate between different domains you own. Without proper configuration, each domain transition creates a new visitor session, fragmenting your analytics data and making conversion attribution impossible.

When Cross-Domain Tracking Is Required

• Multi-domain journeys: Main site to checkout subdomain (e.g., www.example.com to checkout.example.com)
• Third-party payment providers: Redirects to payment gateways that return users to your confirmation page
• Microsites and campaign landing pages: Promotional sites that funnel users to the main conversion domain
• International domains: Country-specific TLDs that share a common user journey (e.g., .com, .co.uk, .de)
• App-to-web transitions: Mobile app deep links that open web content in a browser

Configuration Steps

Using setDomains

Add all domains that should share visitor sessions to the setDomains configuration:

_paq.push(['setDomains', [
  '*.example.com',
  '*.checkout.example.com',
  'payments.thirdparty.com'
]]);

The asterisk wildcard includes all subdomains. List the primary domain first as it becomes the cookie domain.

Enabling the Cross-Domain Linker

For Matomo Tag Manager deployments:

1. Navigate to Variables and create a constant variable containing your domain list
2. In your Matomo Configuration tag, enable Enable cross domain linking
3. Add all domains to the Domains field, comma-separated
4. The linker automatically appends pk_vid parameters to cross-domain links

For direct JavaScript implementation:

_paq.push(['enableCrossDomainLinking']);
_paq.push(['setDomains', ['*.example.com', '*.partner-site.com']]);

Referral Exclusions

Prevent sibling domains from appearing as traffic sources:

1. In Matomo, go to Administration > Websites > Manage
2. Select your site and navigate to Excluded Parameters
3. Add all domains participating in cross-domain tracking to Excluded Referrers

This ensures users returning from checkout or payment domains retain their original attribution.

Third-Party Checkout Handling

When users redirect to external payment providers (Stripe, PayPal, Adyen):

1. Pre-redirect capture: Store the Matomo visitorId in a server-side session or pass it as a URL parameter to the payment provider
2. Return URL configuration: Include the pk_vid parameter in the return/callback URL from the payment provider
3. Post-redirect restoration: Matomo automatically reads the pk_vid parameter and restores the visitor session

Example return URL structure:

https://example.com/order-confirmation?pk_vid=abc123xyz789&order_id=12345

Edge Cases and Considerations

Cookie Consent Impact

Cross-domain linking requires cookies to be accepted. For cookieless tracking:

• The linker still works but relies entirely on URL parameters
• Session continuity may be less reliable without persistent cookies
• Consider first-party data strategies for high-value conversions

Link Decoration Blockers

Some browsers and privacy extensions strip URL parameters:

• Implement server-side session stitching as a fallback
• Use first-party subdomains where possible to reduce parameter reliance
• Monitor cross-domain conversion rates for anomalies indicating blocking

iFrame Embeds

When embedding content via iframes across domains:

• Parent and child frames must both have Matomo tracking
• Use postMessage to pass visitor identifiers between frames
• Consider whether the embedded content genuinely needs tracking

Validation Steps

Pre-Launch Testing

1. Tag Manager Preview: Enable Matomo Tag Manager preview mode and navigate through cross-domain flows
2. Network inspection: Verify pk_vid parameters appear on cross-domain links in browser DevTools
3. Real-Time dashboard: Confirm a single visitor session spans multiple domains
4. Cookie inspection: Check that the _pk_id cookie domain matches your configuration

Post-Launch Monitoring

• Compare pre- and post-implementation session counts per domain
• Review conversion attribution reports for accuracy
• Check that referral traffic from internal domains has dropped to near zero
• Validate ecommerce funnel completion rates across domain transitions

Troubleshooting Common Issues