API stands for application programming interface, which is a set of definitions and protocols for building and integrating application software. APIs allow developers to save time by taking advantage of a platform’s implementation to do the nitty-gritty work. This helps reduce the amount of code developers need to create, and also helps create more consistency across apps for the same platform. In basic terms, APIs are a set of functions and procedures that allow for the creation of applications. They access the data and features of other applications, services, or operating systems. For instance, Twilio launched its API-as-a-product platform in 2007, which allowed developers to make and receive phone calls from any cloud application.

• In recent years, the OpenAPI specification has emerged as a common standard for defining REST APIs.
• This means that the only way for traffic to leave a network is through the API gateway, using approved external APIs.
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For example, modern APIs make substantial use of HTTP, which has undergone significant changes—HTTP/2 adoption is becoming established, and the HTTP/3 specification has been developed. But as the standards evolve, new API techniques are also evolving to exploit the newer api explanation standards. Here are some API examples from existing platforms with open APIs (the leading standard for REST-based API definitions) that can be explored by anyone. Find out everything you need to know about building an enterprise API strategy with this comprehensive guide.

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The calls that make up the API are also known as subroutines, methods, requests, or endpoints. An API specification defines these calls, meaning that it explains how to use or implement them. In a layered system architecture, the client can connect to other authorized intermediaries between the client and server, and it will still receive responses from the server. You can design your RESTful web service to run on several servers with multiple layers such as security, application, and business logic, working together to fulfill client requests.

For example, traffic app Waze uses APIs to exchange data with local government agencies and other partners about road closures, accidents, and other factors that impact traffic. API software lets the components of two applications talk to each other using a set of simple commands. Essentially, APIs are messengers that deliver requests and return responses between applications.

Advanced API gateway use cases

Application programming interfaces (APIs) have been around for many years. Developers have been working with APIs in the form of Java and C# Interfaces, Python’s Abstract Base Classes, and Rust’s Traits. The goal is always to establish an agreement or contract through which different pieces of code can exchange data with each other. But rather than using the mechanisms in the programming language to enable the communication, we use (sometimes built-in) libraries to use web technologies such as HTTP. As a result, implementations of Web APIs using these technologies are often referred to as web services. Web API calls can come from any programming language, but webpages created in HTML or application generator tools can also make them.

An application programming interface (API) defines the rules that you must follow to communicate with other software systems. Developers expose or create APIs so that other applications can communicate with their applications programmatically. For example, the timesheet application exposes an API that asks for an employee’s full name and a range of dates. When it receives this information, it internally processes the employee’s timesheet and returns the number of hours worked in that date range. The primary difference between the two comes down to implementation, not goals. SOA generally leverages SOAP and its complexity while microservices leverage REST and more modern protocols.