What is an Application Programming Interface (API)?

An Application Programming Interface (API) defines established protocols together with its associated tools and rules, which permit software programs to share data securely. They also function as an access control system that allows users to interact with app features while protecting the app’s underlying code and database structures.

For instance, a payment gateway API such as Stripe or PayPal enables mobile applications to conduct financial transactions while keeping their internal processing systems secure. Likewise, a weather API provides temperature information to different applications, which use different techniques to record and preserve their data.

How do APIs work?

APIs work through their request and response system. The API endpoint receives a request from a client, which can be either a mobile or a web application. They then process the request internally and return an organized response that typically uses JSON or XML document formats.

Key components include:

1. Client: Initiates the request (app, website, IoT device).
2. Endpoint: Specific URL representing a function or resource (e.g., /users/{id}).
3. HTTP Methods: GET to retrieve data, POST to create, PUT/PATCH to update, DELETE to remove.
4. Authentication: Via API keys, OAuth tokens, or JWTs to ensure secure access.
5. Response Handling: returns data and status codes (i.e., 200 OK, 400 Bad Request, 401 Unauthorized).

For instance, ride-hailing apps utilize multiple APIs like mapping APIs to calculate routes in real time, pricing APIs to determine fares, and payment APIs to handle pre-authorization processes.

What is the main purpose of using an API?

The main functions of APIs include:

• System Integration: The system enables multiple applications to connect with each other through its API interface. For example, an Enterprise Resource Planning or ERP system uses APIs to synchronize customer data with CRM platforms through this functionality.
• Modularity and Scalability: APIs enable microservices architectures to achieve independent service expansion through authentication, analytics, and notification services.
• Security and Control: APIs grant users restricted access to resources, which decreases security risks compared to allowing direct database access.
• Innovation: Public APIs enable developers from outside the organization to build new applications that operate on established platforms, as seen with fintech, social media, or e-commerce ecosystems.

APIs drive digital transformation as they enable organizations to share real-time data while their authentication works and their systems maintain existing functions.

What are the types of APIs?

APIs can be classified by access and architecture:

1. Public APIs: Also called Open APIs, they let external developers access them while they provide weather data, social media content, and mapping functions.
2. Private APIs: They function as internal systems that connect backend resources with internal applications to support their operations.
3. Partner APIs: These APIs act as shared resources that businesses use to establish supply chain and payment integrations between their organizations.
4. REST APIs: These operate through HTTP methods while maintaining a stateless connection, which supports their application in web and mobile platforms.
5. SOAP APIs: They function through XML-based systems, following the established protocols that organizations use in financial and enterprise environments.
6. GraphQL APIs: They enable clients to obtain precisely what they want through a single request, reducing over-fetching or under-fetching.

Each API type addresses different needs, from internal automation to third-party integration, balancing flexibility, performance, and security.