Server-to-server (S2S)

What is Server-to-server (S2S)?

Server-to-server (S2S) tracking is a data transmission method where information flows directly between servers without relying on client-side technologies like SDKs or cookies. When a user clicks a tracking link, a unique identifier is created and stored, then transmitted server-to-server when conversions occur, enabling attribution partners to match user activities and attribute conversions accurately.

How it works

S2S tracking operates through a secure server-to-server communication protocol that bypasses client-side limitations. When a user interacts with an ad, the advertising platform generates a unique click ID and stores it on their server. Upon conversion, the app server sends this identifier along with conversion data directly to the measurement partner's server via API calls. This creates a closed-loop system where data flows between trusted servers without exposure to client-side vulnerabilities.

Data Flow Process

The S2S process begins when users engage with ads, creating unique identifiers that link their journey from impression to conversion. App servers collect conversion events and package them with matching identifiers, then transmit this data through secure HTTP requests to attribution platforms. The receiving server validates the data, performs attribution logic, and sends confirmation back to complete the tracking loop.

Implementation Requirements

Successful S2S implementation requires robust server infrastructure, secure API endpoints, and proper data formatting protocols. Organizations must establish authentication mechanisms, implement retry logic for failed transmissions, and maintain consistent data schemas across all server communications.

Why it matters

S2S tracking provides enhanced data security and privacy compliance while maintaining attribution accuracy in an increasingly regulated digital landscape. Unlike SDK-based tracking, S2S reduces app bloat by eliminating multiple third-party code integrations, improving app performance and user experience. S2S implementations reduce app binary size, improve security by keeping sensitive data server-side, and provide greater flexibility in data processing compared to multi-SDK approaches. This method also offers superior protection against ad fraud, as server-side validation makes it significantly harder for malicious actors to manipulate tracking data. For mobile marketers facing iOS 14.5+ attribution challenges, S2S is one component of a privacy-compliant measurement stack. Combined with SKAdNetwork and first-party identifiers (such as IDFV or custom user IDs), S2S enables event tracking without relying on IDFA, though it does not replace ATT consent requirements or enable cross-app tracking on its own.

How to Implement Server-to-Server Tracking

Start by establishing secure API endpoints on your app servers that can receive and process conversion events. Configure your server infrastructure to handle authentication tokens and implement proper error handling for failed transmissions. Set up data formatting protocols that match your attribution partner's requirements, ensuring all conversion events include necessary identifiers like click IDs, timestamps, and user parameters.

Next, integrate S2S postback URLs with your advertising platforms to receive click data and impression identifiers. Test data transmission flows using sandbox environments before deploying to production, validating that conversion events properly match with click identifiers. Implement monitoring systems to track transmission success rates and identify any data discrepancies.

Finally, establish backup mechanisms for data retention and implement retry logic for failed API calls. Modern MMPs like Airbridge provide comprehensive S2S integration support with detailed documentation and testing tools to ensure seamless implementation. Regular monitoring and optimization of your S2S setup ensures continued accuracy and performance as your user base grows.

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