In today’s ultra-connected world, consumers interact with brands across various touch points–including multiple devices (desktop, mobile, apps, etc.) and across multiple sessions over time. This creates a fragmented view of customer journeys, making it difficult for marketers to provide a consistent experience, accurately attribute conversions, and target (or retarget) ads effectively. Worse, a high volume of anonymous traffic makes this new reality exponentially more challenging.  

Identity stitching, or linking user data across devices and channels, addresses this challenge by expanding addressable audience sizes and creating unified customer profiles. This approach not only helps improve retargeting and attribution but also provides more opportunities to engage high-value segments and drive revenue growth.

But how can you unify customer identities and build a seamless user experience? To better understand how this works, we’ll explore the concept of identity stitching and how using an identity graph as part of this strategy can be a game-changer for your marketing efforts.‍

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What is an Identity Graph?

An identity graph is a tool that collects and organizes data about an individual across multiple devices, channels, and platforms in one unified customer profile. This graph connects both online and offline identifiers—such as device IDs, email addresses, cookies, IP addresses, and even behavioral data—to create a comprehensive view of the customer. By linking these data points, brands can achieve cross-device identification, meaning they can recognize the same individual whether they’re using a laptop, smartphone, or tablet.

How Identity Stitching Works

Identity stitching leverages the data within an identity graph to match user identifiers across multiple touchpoints. Here’s how it works:

1. Data Collection: First, data is collected from various sources, including cookies, device IDs, email addresses, login information, and even offline data, such as phone numbers or loyalty card usage. Compiling this information helps you capture interactions across all channels—both online and offline.
2. Matching and Linking: Identity stitching then compares and matches these identifiers across platforms and devices to build a singular, unified customer profile. Deterministic matching techniques can link profiles through shared identifiers like an email login, while probabilistic matching uses patterns such as location, browsing behavior, and IP addresses to create likely matches across devices.
3. Persistent Identifiers: The use of persistent identifiers (which last over 12 months) enables brands to continue tracking and engaging users with consistent experiences, even after long periods of inactivity. This bypasses the need for frequent touchpoints or site visits to maintain the connection.
4. Cross-Device and Cross-Channel View: Once user identities are stitched together, brands can see a single customer journey that spans multiple devices, enabling them to engage users more effectively and measure performance across touchpoints.

There is non-sustainable way to stitch user identities together and a future-proofed way. Let’s take a look at each.

The Non-Sustainable Way: Start with PII, Match IPs, and Fill Gaps

Historically, marketers have relied on Personally Identifiable Information (PII), such as names, email addresses, and phone numbers, to identify and target users. While PII remains valuable, it presents limitations, especially in today’s privacy-centric digital landscape. To fill the gaps, many brands have started supplementing PII with secondary data like IP addresses, device IDs, and cookies to try and stitch together fragmented customer identities. However, this method is becoming increasingly ineffective due to browser restrictions, ad blockers, and tightening privacy regulations.

Furthermore, PII-based targeting requires explicit user consent and often misses the vast majority of anonymous users who have not yet provided personal information or opted into marketing communications. Additionally, IP addresses are often temporary and shared across multiple users, making them unreliable as long-term identifiers.

Most companies have taken this more straightforward approach to identity resolution because it’s easier. They start with PII and fill in the gaps by matching IP addresses and using fingerprinting methods where necessary. It works, but it’s a puzzle with missing pieces. Why? Because starting with PII has limitations in the age of increasing privacy concerns:

• Privacy regulations: New laws, like the General Data Protection Regulation (GDPR) and California Consumer Protection Act (CCPA), heavily regulate the collection of IP addresses and other PII.
• Limited scalability: Relying on PII doesn’t account for the ever-changing methods of user interaction across devices, making it difficult to build a consistent identity.
• Incomplete insights: IP address matching and fingerprinting are stopgaps, not long-term solutions. They can offer partial views of the user, but they fail to provide the full picture in a privacy-compliant way.

While this easy route might work for some, it leaves companies vulnerable to regulatory risks and an incomplete identity framework that ultimately limits how deeply they can understand their users.

The Future-Proofed Way: Reconstruct Identity with a Privacy-Forward Approach

The more complex yet future-proof approach to identity resolution is to rethink how identity is negotiated in the first place—without relying on PII. This paradigm shift starts with a foundational element in the digital ecosystem: tags.

Tags have been central to identity resolution for years, but the challenge now is to deconstruct how they work and reconstruct them in a privacy-first way. This means streamlining data collection directly from the browser while routing that data server-side. Why is this “trickier”? Because every vendor has its own ID ecosystem, so it’s comparably more difficult to integrate identity resolution across platforms.

• Google IDs, Facebook IDs, and beyond: Each of these ecosystems has its own methods of identifying users, and they don’t always play well together. Understanding how each ID system operates and how to integrate them with server-side behavioral data requires extensive trial and error.
• Vendor-specific challenges: Instead of matching IP addresses or using PII, this method involves passing along vendor-specific IDs (from cookies, URL parameters, etc.) that can only be resolved within each platform’s ecosystem. This complexity requires deep technical expertise.

But the payoff is worth it: a privacy-compliant identity resolution framework that works across platforms and devices without violating privacy regulations. And it provides more accurate, 1:1 identity matching, minimizing wasted ad spend and maximizing ROI.

Here’s How It Works

1. Vendor IDs and Contextual Data: When a user interacts with a website, app, or digital platform, a unique Vendor ID is created based on first-party data. This ID captures key information, such as device type, location, browsing behavior, and session activity—all without requiring the user to provide PII.
2. Real-Time Identity Negotiation: Modern identity solutions can exchange these Vendor IDs across various systems and partners in real time. This enables brands to recognize and address users across multiple channels—even when they remain anonymous. By synchronizing Vendor IDs across the ecosystem, brands can build a unified, persistent profile for users as they engage with different touchpoints.
3. Privacy-Centric Approach: Unlike traditional PII-based methods, this approach respects user privacy. Since no personal information is collected or shared, it remains compliant with privacy regulations such as GDPR and CCPA. This provides a scalable way for brands to reach anonymous users, expand their addressable audience, and drive engagement without infringing on user consent.

How This Works With Other Tools

CDP Enhancement: Increase Addressability and Reach

For brands with significant anonymous user traffic, identity stitching offers a powerful way to expand addressable audience sizes within a CDP. By leveraging persistent identifiers that last over 12 months, brands can avoid needing to re-engage users every seven days. This method also bypasses ad blockers and browser limitations, capturing both anonymous and known user data to create more complete customer profiles and give marketers more opportunities to engage high-value segments, optimize performance, and ultimately drive revenue by ensuring that every interaction is effectively attributed and activated.

The results? 3-5x addressable audiences within your CDP for retargeting and segmentation efforts.

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Analytics Tools

Let’s use GA4 as an example. The unified identity stitching provided by our patent-pending Sync Injector ensures that user journeys are accurately tracked, offering a complete view of user behavior across platforms in both GA4 and BigQuery. This improves the accuracy of cohort analysis, attribution models, and audience segmentation.  

The Sync Injector also enhances data streams by adding custom business logic, attributes, and enrichment before the data reaches GA4 and BigQuery.  This means you can pre-process data with additional context—such as calculated metrics, external data sources, or customer lifetime value (CLV, pCLV)—and then forward this enriched data into GA4 and BigQuery.

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Making Anonymous Users Addressable Without PII

The ability to make anonymous users addressable in a privacy-compliant way is a game-changer for marketers. By negotiating Vendor IDs across the ecosystem, brands can:

• Increase Reach: Brands no longer need to wait for users to log in or provide personal information to identify and target them. Instead, they can leverage Vendor IDs to recognize users and engage them from the very first interaction.
• Achieve Cross-Device Targeting: These modern solutions enable cross-device tracking without relying on PII or cookies. As users move between devices, Vendor IDs can stitch their actions together to form a unified customer profile, allowing for consistent engagement across touchpoints.
• Improve Real-Time Personalization: By negotiating Vendor IDs in real time, marketers can deliver personalized ads and experiences to users based on their immediate behavior and preferences, even when those users remain anonymous.
• Future-Proofing for Privacy: As privacy laws continue to evolve, solutions that minimize the reliance on PII are becoming increasingly essential. Vendor ID-based identity resolution is a forward-thinking approach that ensures compliance while maximizing audience targeting capabilities.

Choosing Comprehensive, Privacy-Forward Identity Resolution

At MetaRouter, we’ve put in the time and effort to figure out this “future-proofed" way of identity resolution. We believe that robust consumer privacy protections are the future, and our platform is designed to excel in this reality while giving you the insights you need to drive business success.

Unlike many platforms, MetaRouter gives you the choice of how to manage identity:

• IP addresses: You can choose whether or not to collect IP addresses. If your privacy policy or regulations require you to avoid IP collection, MetaRouter’s UI clearly indicates whether IP data is being collected. But here’s the key: You don’t need IP addresses to resolve anonymous identities.
• Vendor-specific IDs: We allow you to collect vendor-specific IDs without sending PII. These IDs—derived from cookies, URL parameters, or device-specific data—are meaningful only within a vendor’s ecosystem. This allows for 1:1 targeting rather than relying on household-level targeting, which can be wasteful and less accurate.

And that’s the game-changer. By avoiding PII, you can achieve identity resolution in a privacy-compliant manner, without sacrificing accuracy or data quality.

The Choice Is Yours

When it comes to identity resolution, there’s the future-proofed way—relying on PII and facing potential regulatory risks—or the future-proof way—deconstructing the identity negotiation process and rebuilding it in a privacy-forward manner.

At MetaRouter, we’ve chosen the future-proof way. And while it’s more complex, it’s also more sustainable and scalable. Identity unification without PII is possible—and it’s the path that privacy-centric, forward-thinking companies are already taking.

The only question left: Which path will you choose?