An API (application programming interface) is a set of rules that allows software applications to communicate with one another. It defines how systems request and exchange data or services, enabling them to work together without accessing each other’s internal code or implementation.
What is an API?
An API (application programming interface) is a mechanism that allows software systems to communicate and share data with each other. It enables one application to access specific features or information from another without needing to understand its internal code.
APIs act as a bridge between two software systems, which lets them share data and functionality seamlessly.
How Do APIs Work?
APIs work by sending a request from an application to a server and receiving a response. This request–response cycle enables software systems to communicate.
When an application needs information or functionality from another system — such as a database or external service — it sends a request to an API endpoint, a defined URL or path where the API receives requests and returns responses. The endpoint acts as an access point to a specific resource or service.
The API processes the request, passes it to the appropriate system and sends back a response — which could be data, an action confirmation or an error message. This allows one system to access another’s functionality without needing to understand its internal implementation.
A key benefit of APIs is decoupling. Because API endpoints serve as stable interfaces, applications that rely on them don’t need to change when the underlying infrastructure does as long as the endpoint specifications remain consistent. This flexibility simplifies integration and scaling across diverse systems.
API Examples
A common example of APIs in use are mobile applications, such as weather apps, social media apps finance apps or GPS apps.
For example, when you open a weather app, it sends a request via an API to a remote server for forecast data. The server processes this request, retrieves the relevant weather information and sends it back to the app, which then displays it on your screen.
API vs. REST API
REST APIs are a type of API that follow the principles of representational state transfer (REST), an architectural style based on stateless client-server communication over HTTP.
RESTful APIs commonly use HTTP methods such as GET, POST, PUT and DELETE. They offer a consistent, scalable way to structure data exchange across distributed systems.
While all REST APIs are APIs, not all APIs follow the REST architectural style.
Frequently Asked Questions
What is the purpose of an API?
APIs allow different software systems to communicate and share data or functionality without requiring full access to each other’s codebases.
What is an API endpoint?
An API endpoint is a specific URL where an API receives requests and sends responses, acting as the access point to a resource.
Is REST the only type of API?
No. While REST is a widely used architecture for designing APIs, other types include SOAP, GraphQL and gRPC.
