What is an application program interface (API)?

API definition and API meaning: An application program interface (API) is a defined set of rules that allows different software systems to communicate. APIs enable applications to request and exchange information, access features, and integrate services, without needing to understand each other’s internal logic. They act as a bridge, allowing developers to connect tools, platforms, and products in a standardized and secure way.

APIs are the backbone of modern software development. They unlock speed, interoperability, and scalability by allowing developers to plug into existing services instead of building every feature from scratch. This enables teams to integrate complex functionality, such as authentication, payments, and location services, quickly and reliably.

Beyond development, APIs help businesses scale by safely exposing specific functionality to internal teams or external partners. This encourages third-party innovation, supports modular system architecture, and creates strategic integration opportunities. Internal APIs improve operational efficiency, while partner APIs enable secure, selective collaboration.

At a broader level, APIs power much of today’s digital experience. Features like social login, embedded maps, and content sharing all rely on APIs to operate across apps and platforms. By reducing fragmentation and improving system interoperability, APIs help deliver smoother user experiences (UX) across mobile and web environments.

Understanding the different types of APIs helps developers and marketers choose the right integration strategy. APIs are typically categorized by access level and intended use:

• Public APIs (external or open APIs) are available to anyone—often used to expand a platform’s ecosystem and enable third-party development.
• Private APIs are restricted to internal use within an organization, supporting internal tools and team workflows.
• Partner APIs are shared with selected external collaborators under strict access controls, commonly used for B2B integrations.
• Composite APIs combine multiple data sources or services into a single request, useful for dashboards and mobile apps that require aggregated information.

In mobile marketing, APIs are essential for sharing and analyzing data across platforms. They allow teams to automate data transfers, reduce manual work, and access real-time campaign and user metrics. This improves reporting accuracy and enables faster, more informed decision-making.

By integrating data from multiple ad networks, analytics tools, and marketing platforms, APIs allow for the creation of a consolidated view of performance. This is especially valuable for growing apps, where visibility across fragmented ecosystems is critical to scaling user acquisition (UA) and optimizing return on ad spend (ROAS).

Adjust’s APIs empower developers and marketers to connect all of their data and automate campaign tracking, reporting, and monetization insights. Teams can pull essential metrics, like installs, sessions, revenue, and in-app events, directly into internal dashboards or BI tools, eliminating the need for manual data handling.

Adjust uses postback APIs to send verified conversion data from ad networks to your dashboard, supporting accurate attribution across all integrated partners. APIs for ad spend and ad revenue allow teams to retrieve cost and monetization data from supported networks, providing a comprehensive view of campaign performance.

To support scalable operations, Adjust also offers APIs to create and manage deep links, configure campaigns, and automate app settings, minimizing reliance on manual dashboard work. All Adjust APIs include secure authentication, permission controls, and rate-limiting to ensure reliable performance and data protection.

Turn complex data into clear insights. Learn how Adjust can power your app performance—schedule a demo.