What is a callback?

A callback, also known as a postback, is a ping (an http or https request) made between one server and another. A callback happens when an activity or event takes place within an app. It can happen manually or automatically.

When a user interacts with an ad or performs an in-app action, a callback is triggered. This sends structured data, such as device ID, event type, and timestamp, from one server to another. Callbacks allow real-time data transfer to analytics platforms, attribution providers, or internal systems.

At Adjust, the SDK detects these events and immediately fires a callback URL containing dynamic placeholders (macros). These placeholders, like advertising ID or app version, are replaced with actual values before the callback is sent.

Adjust callbacks can include attribution details, app-specific parameters, or (consented) identifiers. They can be triggered by ad engagements (via the tracker URL) or in-app events (via the SDK). This ensures accurate, immediate delivery of raw event data to your server.

The diagram below shows how this event data flows through Adjust’s system to your backend.

Callbacks are extremely important for performance-driven mobile marketing. They provide the essential, real-time data delivery between mobile apps and backend systems, which, in turn, enables accurate reporting, automated optimization, and data syncing across platforms.

Callbacks are also critical for dashboards and analytics tools that rely on precise, event-level data. Because callbacks are triggered immediately, developers and marketers can act on user behavior as it happens—whether it's a crash report, in-app purchase (IAP), or a key funnel event.

Callbacks play a key role in real-time performance tracking across the mobile app lifecycle. Here are some of the most effective ways to use them:

• Track IAPs to measure ROAS: Monitor when a user completes a purchase and attribute revenue to campaigns or cohorts instantly.
• Measure push notification effectiveness: Capture callback events triggered by user re-engagement after a push to evaluate campaign lift.
• Receive crash report callbacks for faster debugging: Get alerted when app crashes occur so your dev team can react immediately and reduce churn.
• Monitor retention and re-engagement behavior: Use callbacks to track returning users, session activity, and retargeting impact in real time.
• Analyze funnel progression by event stage: Set up callbacks for each conversion step (e.g., install → registration → trial) to measure where users drop off.

While it's technically possible to trigger callbacks for nearly every tracked event, doing so is rarely practical or optimal. Callback configurations should be carefully planned to ensure system efficiency and data quality.

One critical consideration is server load. Sending callbacks for every event, especially in high-traffic apps, can overwhelm backend systems. This may introduce latency or disrupt other processes that rely on the same infrastructure. A second concern is data relevance. When too many low-priority events are tracked, it becomes harder to identify meaningful signals. Excessive callbacks can lead to cluttered analytics and slower decision-making.

A more effective approach is to trigger callbacks at specific, high-value moments in the user journey, such as installs, registrations, purchases, and re-engagements. This offers a balanced view of user behavior while preserving system performance and analytical clarity. Structured callback planning at key conversion points supports better retargeting, funnel diagnostics, and campaign optimization.

To ensure callback setups are efficient, accurate, and scalable, follow these core practices:

• Start with high-priority events: Only trigger callbacks for key actions like installs, registrations, IAP, re-engagements, or crashes, where real-time data has the most impact on decision-making and LTV modeling.
• Keep callback payloads lean: Use only the most relevant placeholders in your URLs to avoid unnecessary data, reduce load, and improve processing speed.
• Prepare your infrastructure: Make sure your servers can handle callback volume during traffic spikes. Add retry logic and monitor for any failed deliveries.
• Test before going live: Run callbacks in a staging environment to confirm proper formatting, value mapping, and delivery to your analytics or BI tools.

Adjust supports multiple types of callbacks to help you integrate app event data with your internal systems. Global callbacks are used for high-level activity such as installs, sessions, and ad clicks. Single activity callbacks are configured for specific in-app events, and multiple callbacks allow the same data to be sent to more than one endpoint.

Each callback can be customized using dynamic placeholders, which are Adjust macros that are replaced in real time with actual values when the callback is triggered. These values can include advertising identifiers, attribution details, app metadata, or custom parameters. You can find Adjust’s recommended list of placeholders here, any of which can be used depending on your use case.

To keep payloads efficient and relevant, it’s best to include only the data fields required for your reporting or integrations. Our Help Center provides technical advice for mobile marketers working with callbacks, including how to select appropriate events, define callback URLs, and connect callback data to your internal systems.

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