MediaMath Cross-Domain Tracking | OpsBlu Docs

MediaMath Cross-Domain Tracking

Configure cross-domain tracking for MediaMath pixels across multiple domains and subdomains.

Overview

Cross-domain tracking enables MediaMath to maintain user attribution and retargeting across multiple domains in your conversion funnel. This is critical for:

  • Main website to separate checkout domain
  • Multiple country-specific domains
  • Third-party payment processors
  • Partner/affiliate websites

MediaMath uses third-party cookies to track users across domains:

  • Cookie Name: mt_mop, mt_misc
  • Domain: .mathtag.com (third-party)
  • Expiration: Configurable in TerminalOne (default 30-90 days)
  • Purpose: User identification and frequency capping

For improved tracking in browsers with third-party cookie restrictions:

// Set first-party cookie with MediaMath user ID
function setMediaMathFirstPartyCookie(userId) {
  var expiryDays = 90;
  var date = new Date();
  date.setTime(date.getTime() + (expiryDays * 24 * 60 * 60 * 1000));
  var expires = "expires=" + date.toUTCString();

  document.cookie = "mm_user_id=" + userId + ";" + expires + ";path=/;domain=.yourdomain.com;SameSite=Lax";
}

// Get first-party cookie
function getMediaMathFirstPartyCookie() {
  var name = "mm_user_id=";
  var decodedCookie = decodeURIComponent(document.cookie);
  var cookieArray = decodedCookie.split(';');

  for (var i = 0; i < cookieArray.length; i++) {
    var cookie = cookieArray[i].trim();
    if (cookie.indexOf(name) === 0) {
      return cookie.substring(name.length, cookie.length);
    }
  }
  return null;
}

Cross-Domain Implementation

Same Pixel Across All Domains

Deploy the same MediaMath universal pixel on all domains:

// Domain A: www.example.com
(function() {
  var mtm = document.createElement('script');
  mtm.type = 'text/javascript';
  mtm.async = true;
  mtm.src = 'https://pixel.mathtag.com/event/js?mt_id=ADVERTISER_ID&mt_adid=PIXEL_ID&mt_exem=&mt_excl=&v1=&v2=&v3=&s1=&s2=&s3=';
  var s = document.getElementsByTagName('script')[0];
  s.parentNode.insertBefore(mtm, s);
})();

// Domain B: checkout.example.com
// Use the SAME pixel configuration
(function() {
  var mtm = document.createElement('script');
  mtm.type = 'text/javascript';
  mtm.async = true;
  mtm.src = 'https://pixel.mathtag.com/event/js?mt_id=ADVERTISER_ID&mt_adid=PIXEL_ID&mt_exem=&mt_excl=&v1=&v2=&v3=&s1=&s2=&s3=';
  var s = document.getElementsByTagName('script')[0];
  s.parentNode.insertBefore(mtm, s);
})();

Subdomain Tracking

For subdomains under the same root domain:

// Set cookie domain to share across subdomains
function setSharedCookie(name, value) {
  var expiryDays = 90;
  var date = new Date();
  date.setTime(date.getTime() + (expiryDays * 24 * 60 * 60 * 1000));
  var expires = "expires=" + date.toUTCString();

  // Note the leading dot for subdomain sharing
  document.cookie = name + "=" + value + ";" + expires + ";path=/;domain=.example.com;SameSite=Lax";
}

Subdomain Examples

www.example.com     → domain=.example.com
app.example.com     → domain=.example.com
checkout.example.com → domain=.example.com

Cross-Domain Parameter Passing

Method 1: URL Parameters

Pass user identifier across domains via URL:

function appendMediaMathId(url) {
  var mmUserId = getMediaMathFirstPartyCookie();

  if (mmUserId) {
    var separator = url.indexOf('?') > -1 ? '&' : '?';
    url += separator + 'mm_uid=' + mmUserId;
  }

  return url;
}

// Apply to cross-domain links
document.addEventListener('DOMContentLoaded', function() {
  var crossDomainLinks = document.querySelectorAll('a[href*="checkout.example.com"]');

  crossDomainLinks.forEach(function(link) {
    link.href = appendMediaMathId(link.href);
  });
});

Method 2: Form Field Injection

For forms submitting to another domain:

function injectMediaMathIdIntoForm(formElement) {
  var mmUserId = getMediaMathFirstPartyCookie();

  if (mmUserId) {
    var hiddenField = document.createElement('input');
    hiddenField.type = 'hidden';
    hiddenField.name = 'mm_uid';
    hiddenField.value = mmUserId;
    formElement.appendChild(hiddenField);
  }
}

// Apply to checkout form
document.addEventListener('DOMContentLoaded', function() {
  var checkoutForm = document.getElementById('checkout-form');
  if (checkoutForm) {
    checkoutForm.addEventListener('submit', function(e) {
      injectMediaMathIdIntoForm(checkoutForm);
    });
  }
});

Server-Side Cross-Domain Tracking

Extract and Forward User ID

// On destination domain, extract mm_uid from URL
function extractMediaMathId() {
  var urlParams = new URLSearchParams(window.location.search);
  var mmUserId = urlParams.get('mm_uid');

  if (mmUserId) {
    setMediaMathFirstPartyCookie(mmUserId);
  }
}

// Call on page load
extractMediaMathId();

Server-Side Implementation (Node.js)

const express = require('express');
const app = express();

app.get('/checkout', (req, res) => {
  const mmUserId = req.query.mm_uid || req.cookies.mm_user_id;

  if (mmUserId) {
    res.cookie('mm_user_id', mmUserId, {
      maxAge: 90 * 24 * 60 * 60 * 1000, // 90 days
      domain: '.example.com',
      httpOnly: false,
      sameSite: 'lax'
    });
  }

  res.render('checkout');
});

Server-Side Implementation (Python)

from flask import Flask, request, make_response

app = Flask(__name__)

@app.route('/checkout')
def checkout():
    mm_user_id = request.args.get('mm_uid') or request.cookies.get('mm_user_id')

    response = make_response(render_template('checkout.html'))

    if mm_user_id:
        response.set_cookie(
            'mm_user_id',
            mm_user_id,
            max_age=90 * 24 * 60 * 60,  # 90 days
            domain='.example.com',
            httponly=False,
            samesite='Lax'
        )

    return response

Third-Party Payment Processors

For payment processors like PayPal, Stripe:

Pre-Redirect Tracking

Fire conversion pixel before redirect:

function trackBeforePaymentRedirect(orderData) {
  // Fire MediaMath pixel before redirect
  var mtm = document.createElement('script');
  mtm.type = 'text/javascript';
  mtm.async = false; // Synchronous to ensure firing before redirect

  var pixelUrl = 'https://pixel.mathtag.com/event/js?' +
    'mt_id=' + encodeURIComponent('ADVERTISER_ID') +
    '&mt_adid=' + encodeURIComponent('CHECKOUT_PIXEL_ID') +
    '&mt_exem=' +
    '&mt_excl=' +
    '&v1=' + encodeURIComponent(orderData.value) +
    '&v2=' + encodeURIComponent(orderData.orderId) +
    '&v3=' + encodeURIComponent('checkout_initiated') +
    '&s1=&s2=&s3=';

  mtm.src = pixelUrl;
  var s = document.getElementsByTagName('script')[0];
  s.parentNode.insertBefore(mtm, s);

  // Add small delay before redirect
  setTimeout(function() {
    window.location.href = orderData.paymentUrl;
  }, 500);
}

Post-Return Conversion

Fire final conversion after payment completion:

// On return URL: /order-confirmation?order_id=12345
function trackPaymentReturn() {
  var urlParams = new URLSearchParams(window.location.search);
  var orderId = urlParams.get('order_id');

  if (orderId) {
    // Fetch order details from server
    fetch('/api/orders/' + orderId)
      .then(response => response.json())
      .then(order => {
        // Fire conversion pixel
        fireMediaMathConversionPixel(order);
      });
  }
}

Multiple Top-Level Domains

For separate TLDs (e.g., example.com, example.co.uk):

Shared User Identification

// Store in localStorage for cross-domain access
function storeMediaMathIdGlobally(userId) {
  if (typeof localStorage !== 'undefined') {
    localStorage.setItem('mm_global_user_id', userId);
    localStorage.setItem('mm_global_timestamp', Date.now());
  }
}

// Retrieve and sync
function syncMediaMathIdAcrossDomains() {
  if (typeof localStorage !== 'undefined') {
    var globalUserId = localStorage.getItem('mm_global_user_id');
    var timestamp = localStorage.getItem('mm_global_timestamp');

    // Check if ID is recent (within 90 days)
    var ninetyDaysAgo = Date.now() - (90 * 24 * 60 * 60 * 1000);

    if (globalUserId && timestamp > ninetyDaysAgo) {
      setMediaMathFirstPartyCookie(globalUserId);
    }
  }
}

syncMediaMathIdAcrossDomains();

Testing Cross-Domain Tracking

function testCrossDomainTracking() {
  console.log('=== MediaMath Cross-Domain Test ===');

  // Check for cookies
  var mmCookies = document.cookie.split(';').filter(cookie => {
    return cookie.trim().startsWith('mm_') || cookie.trim().indexOf('mt_') > -1;
  });

  console.log('MediaMath Cookies:', mmCookies);

  // Check first-party cookie
  var fpCookie = getMediaMathFirstPartyCookie();
  console.log('First-Party Cookie:', fpCookie);

  // Check localStorage
  if (typeof localStorage !== 'undefined') {
    console.log('LocalStorage ID:', localStorage.getItem('mm_global_user_id'));
  }

  console.log('===================================');
}

testCrossDomainTracking();

Browser Developer Tools

  1. Open Developer Tools
  2. Go to Application tab
  3. Check Cookies for both domains
  4. Verify third-party cookies from .mathtag.com
  5. Check first-party cookies on your domain

Privacy Considerations

GDPR Compliance

// Only fire pixels with user consent
function fireMediaMathPixelWithConsent(pixelId, data) {
  if (window.gdprConsent && window.gdprConsent.advertising) {
    fireMediaMathPixel(pixelId, data);
  } else {
    console.log('MediaMath pixel blocked - no consent');
  }
}

With Safari ITP and Firefox ETP:

// Detect third-party cookie support
function detectThirdPartyCookieSupport(callback) {
  var iframe = document.createElement('iframe');
  iframe.style.display = 'none';
  iframe.src = 'https://pixel.mathtag.com/cookie-test.html';

  iframe.onload = function() {
    // Send message to check cookie
    iframe.contentWindow.postMessage('test', '*');
  };

  window.addEventListener('message', function(event) {
    if (event.origin === 'https://pixel.mathtag.com') {
      callback(event.data.cookieSupported);
    }
  });

  document.body.appendChild(iframe);
}

// Use fallback if third-party cookies blocked
detectThirdPartyCookieSupport(function(supported) {
  if (!supported) {
    console.log('Third-party cookies blocked - using first-party fallback');
    // Implement first-party cookie strategy
  }
});

Best Practices

  • Deploy same MediaMath pixel ID across all domains for consistent tracking
  • Use first-party cookies as fallback for third-party cookie restrictions
  • Pass user identifiers via URL parameters for critical cross-domain flows
  • Fire pixels before redirects to third-party payment processors
  • Test cookie persistence across all domains in your funnel
  • Implement consent management before setting cookies
  • Document your cross-domain setup and cookie strategy
  • Monitor cookie drop rates across different browsers
  • Use server-side tracking for critical conversions
  • Regularly audit cross-domain tracking after site updates
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