Microsoft Clarity Cross-Domain Tracking | Blue Frog Docs

Microsoft Clarity Cross-Domain Tracking

Configure Microsoft Clarity to track users across multiple domains and subdomains

Microsoft Clarity Cross-Domain Tracking

Overview

Cross-domain tracking lets you follow user journeys that span multiple domains or subdomains. For example, if your main site is on example.com but checkout happens on shop.example.com or checkout.thirdparty.com, cross-domain tracking ensures Clarity treats these as a single continuous session instead of two separate visits.

This guide explains how Clarity handles cross-domain scenarios, when you need special configuration, and how to implement it correctly.

How Clarity Handles Multiple Domains

Default Behavior: Automatic Subdomain Tracking

Clarity automatically tracks users across subdomains of the same root domain without any configuration.

Works automatically:

  • www.example.com → blog.example.com ✅
  • app.example.com → shop.example.com ✅
  • example.com → subdomain.example.com ✅

Clarity uses first-party cookies on the root domain (.example.com), so sessions persist across all subdomains naturally.

No action required. Just install Clarity on all subdomains with the same Project ID.

When Cross-Domain Configuration Is Needed

Cross-domain tracking requires configuration when the user journey crosses different root domains:

Requires configuration:

  • example.com → examplestore.com ❌
  • example.com → checkout-provider.com ❌
  • example.com → partner-site.com ❌

These scenarios require passing session identifiers between domains via URL parameters or postMessage APIs.

When to Use Cross-Domain Tracking

Common Scenarios

1. Separate Checkout Domains

  • Main site: example.com
  • Checkout: secure-checkout.com (third-party payment processor)

2. Multi-Brand Properties

  • Brand A: brand-a.com
  • Brand B: brand-b.com
  • User navigates between brands

3. Marketing Funnels Across Domains

  • Landing page: marketing-campaign.com
  • App signup: app.mainproduct.com

4. Partnerships and Referrals

  • Partner site: partner.com
  • Your product: yourproduct.com

When NOT to Use Cross-Domain Tracking

Subdomains of the same root domain:

  • Already works automatically
  • No configuration needed

Completely separate user journeys:

  • If users on different domains are separate audiences with no overlap
  • Tracking them together provides no value

Limitations of Cross-Domain Tracking in Clarity

Unlike Google Analytics, Microsoft Clarity does not have native cross-domain tracking features built into the platform.

What This Means

  • No automatic cross-domain linker parameters
  • No built-in configuration UI for cross-domain setup
  • Session continuity across different root domains requires manual implementation

Workarounds

While Clarity doesn't support cross-domain tracking natively, you can maintain session continuity using:

  1. Shared User IDs: Identify the same user across domains
  2. Manual URL parameters: Pass session context between domains
  3. Separate projects with manual correlation: Track each domain separately and manually link sessions

Workaround 1: Shared User Identification

The most practical approach is to use clarity("identify") with the same user ID across both domains.

How It Works

  1. Generate a unique user identifier (e.g., from your authentication system or a first-party cookie)
  2. Pass this identifier to both domains
  3. Call clarity("identify", userId) on both domains with the same ID
  4. In Clarity, filter sessions by this user ID to see their cross-domain journey

Implementation

Domain A (example.com):

// Generate or retrieve a unique user ID
let userId = getCrossDomainUserId(); // Your function to generate/retrieve ID

// Identify the user in Clarity
clarity("identify", userId);

// When linking to Domain B, include userId in URL
function navigateToDomainB() {
  window.location.href = `https://checkout.com/?userId=${userId}`;
}

Domain B (checkout.com):

// Extract userId from URL parameter
const urlParams = new URLSearchParams(window.location.search);
const userId = urlParams.get('userId');

if (userId) {
  // Identify the user with the same ID
  clarity("identify", userId);
}

getCrossDomainUserId() Example

function getCrossDomainUserId() {
  // Check if userId exists in localStorage
  let userId = localStorage.getItem('cross_domain_user_id');

  if (!userId) {
    // Generate new UUID
    userId = 'user_' + Date.now() + '_' + Math.random().toString(36).substr(2, 9);
    localStorage.setItem('cross_domain_user_id', userId);
  }

  return userId;
}

Filtering Sessions in Clarity

Once users are identified:

  1. Go to Clarity dashboard > Recordings
  2. Filter by User ID or create custom tags
  3. See all sessions for a specific user across both domains

Note: You'll see separate session recordings for each domain, but they'll be linked by the same user ID.

Workaround 2: Custom URL Parameters

Pass Clarity session metadata between domains via URL parameters.

How It Works

  1. On Domain A, capture key session context (user ID, campaign, source, etc.)
  2. Append this data as URL parameters when linking to Domain B
  3. On Domain B, extract parameters and set them as Clarity custom tags
  4. Filter sessions in Clarity by these tags to correlate cross-domain journeys

Implementation

Domain A (example.com):

// Tag session with context
clarity("set", "entry_domain", "example.com");
clarity("set", "user_journey", "checkout_flow");

// When navigating to Domain B, pass context
function goToCheckout() {
  const context = {
    journey: "checkout_flow",
    referrer: "example_com",
    sessionId: generateSessionId() // Your session ID
  };

  const params = new URLSearchParams(context).toString();
  window.location.href = `https://checkout.com/?${params}`;
}

Domain B (checkout.com):

// Extract context from URL
const urlParams = new URLSearchParams(window.location.search);
const journey = urlParams.get('journey');
const referrer = urlParams.get('referrer');
const sessionId = urlParams.get('sessionId');

// Set Clarity tags to enable filtering
if (journey) clarity("set", "user_journey", journey);
if (referrer) clarity("set", "entry_domain", referrer);
if (sessionId) clarity("set", "linked_session_id", sessionId);

Analyzing Cross-Domain Journeys

  1. In Clarity, filter by custom tags like user_journey: checkout_flow
  2. See sessions from both domains that share the same journey context
  3. Manually review recordings to understand the full user experience

Workaround 3: Separate Projects with Manual Correlation

Use different Clarity projects for each domain and manually correlate sessions.

How It Works

  1. Create separate Clarity projects for each domain
  2. Install each project's tracking code on its respective domain
  3. Use shared identifiers (user ID, order ID, email hash) to manually link sessions

Implementation

Domain A (example.com) – Clarity Project A:

// Clarity Project A
(function(c,l,a,r,i,t,y){
  // ... Clarity code ...
})(window, document, "clarity", "script", "PROJECT_A_ID");

// Tag with shared identifier
clarity("set", "order_id", "12345");
clarity("identify", "user_abc");

Domain B (checkout.com) – Clarity Project B:

// Clarity Project B
(function(c,l,a,r,i,t,y){
  // ... Clarity code ...
})(window, document, "clarity", "script", "PROJECT_B_ID");

// Tag with the same identifier
clarity("set", "order_id", "12345");
clarity("identify", "user_abc");

Analysis Workflow

  1. In Project A, filter by order_id: 12345 or user_id: user_abc
  2. In Project B, filter by the same identifier
  3. Manually review sessions from both projects
  4. Piece together the full user journey

Pros:

  • Clear separation of domains
  • Independent analytics per property

Cons:

  • No single unified view
  • Manual work to correlate sessions

Best Practices

Use Hashed or Anonymized User IDs

Never pass PII (personally identifiable information) in URLs or Clarity identifiers.

❌ Don't:

clarity("identify", "user@email.com"); // PII!

✅ Do:

const hashedId = hashFunction("user@email.com");
clarity("identify", hashedId);

Consistent Naming Conventions

Use the same custom tag names across all domains:

// Domain A
clarity("set", "journey_stage", "awareness");

// Domain B
clarity("set", "journey_stage", "checkout"); // Same tag name, different value

This makes filtering and analysis consistent.

Document Your Cross-Domain Setup

Maintain documentation that includes:

  • Which domains are linked
  • What user ID or session ID scheme is used
  • Which Clarity projects track which domains
  • How to filter and correlate sessions

Example documentation:

Domain Clarity Project User ID Scheme Notes
example.com Project A (abc123) user_{timestamp}_{random} Main site
checkout.com Project B (xyz789) Same as Domain A Checkout flow

Test Cross-Domain Flows

  1. Navigate from Domain A to Domain B
  2. Check that user ID or session context is passed correctly
  3. Verify Clarity tags are set on Domain B
  4. Confirm you can filter sessions in Clarity dashboard

Alternative: Use Google Analytics for Cross-Domain

If you need robust cross-domain tracking, consider:

  1. Use Google Analytics 4 for cross-domain tracking (it has native support)
  2. Integrate Clarity with GA4 to get session recordings for cross-domain users
  3. Filter Clarity by GA dimensions (campaign, source, medium)

This way, GA4 handles cross-domain session continuity, and Clarity provides the behavioral insights for those sessions.

Setup Steps

  1. Configure GA4 cross-domain tracking (GA4 docs)
  2. Link Clarity with GA4 (Integration guide)
  3. In Clarity, filter recordings by GA4 dimensions to see cross-domain user journeys

Troubleshooting

User IDs Not Matching Across Domains

Symptoms: Different sessions on each domain despite passing user ID

Causes:

  • User ID not extracted correctly from URL on Domain B
  • localStorage blocked by browser privacy settings
  • Typo in user ID parameter name

Fix:

  • Log user ID in console to verify it's being passed and received
  • Use URL parameters instead of localStorage for cross-domain data
  • Ensure parameter names match exactly

Sessions Still Separate in Clarity

Expected behavior: Clarity treats each domain as a separate session

Workaround: Use filters and custom tags to manually group related sessions

Privacy Concerns with URL Parameters

Issue: Passing user IDs in URLs exposes them in browser history, referrer headers, logs

Fix:

  • Hash or encrypt user IDs before passing
  • Use server-side session matching instead of client-side URL params
  • Consider using postMessage API for client-side cross-domain communication (advanced)

Summary

Microsoft Clarity does not have native cross-domain tracking like Google Analytics. However, you can maintain session continuity using:

  1. Shared user identification with clarity("identify")
  2. Custom URL parameters to pass session context
  3. Separate projects with manual correlation

For most use cases, shared user identification is the simplest and most effective approach. For more complex needs, integrate Clarity with Google Analytics 4 and leverage GA4's native cross-domain features.

Additional Resources:

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