What is a web API?

A web API, or web application programming interface, is a set of rules and protocols that allows software applications to communicate with one another over the internet. The defining feature of a web API is that it is accessed through the web using the HTTP protocol, which is the foundation of data communication on the World Wide Web. This enables developers to create applications that can interact with web services, retrieve data, and perform operations remotely.

When designing software, utilizing a web API means that different applications, regardless of their underlying technology stack, can seamlessly communicate over the web. This is particularly valuable for integrating different systems, allowing developers to leverage existing services rather than building everything from scratch.

The other options do not accurately capture the essence of a web API. An application interface for databases focuses more on database management systems rather than web-based interaction. A protocol for designing user interfaces relates to user experience and design principles, which is not the primary function of a web API. Lastly, a tool for data encryption concerns securing data rather than facilitating software communication.