An API (Application Programming Interface) is a set of rules and ready-made functions by which one program can access the capabilities of another. Instead of writing everything from scratch, a developer uses the "building blocks" that a service provides through its API.

Thanks to APIs, many familiar products have become possible: mapping services, mobile and desktop social-network clients, and payment integrations. They all work because the corresponding platforms open up well-designed and thoroughly documented interfaces for third-party applications.

APIs in the crypto industry

• Obtaining quotes and market data from exchanges.
• Automating trading and running trading bots.
• Connecting wallets, payment gateways, and analytics services.

For a user, an API most often stays "behind the scenes," but it is precisely what links different services into a single ecosystem. The clearer and more stable the interface, the easier it is to build reliable applications on its basis.