What is API?

API, which stands for “Application programming interface”, is a set of routines, protocols, and tools for building software applications.

Useful tools

• Apiary - API Design Stack built for developers.
• Swagger - Swagger is a simple yet powerful representation of your RESTful API.

Documenting

• ApiBlueprint - A powerful, high-level API description language for web APIs.

See also

Useful frameworks, libraries, and reading material for building APIs.

• API Platform - API-first web framework on top of Symfony with JSON-LD, Schema.org and Hydra support.
• Apigility - An API builder built with Zend Framework 2.
• DC4D - Building APIs developers will love and use, free video tutorials about APIs. Registration required though.
• HAL - A HAL (Hypertext Application Language) builder library.
• Insomnia - Free REST API client.
• Negotiation - A content negotiation library.
• Undisturbed REST: A Guide to Designing the Perfect API
• Lumen: The stunningly fast micro-framework by Laravel.
• Slim: Slim is a PHP micro framework that helps you quickly write simple yet powerful web applications and APIs.
• API Security Checklist - Checklist of the most important security countermeasures when designing, testing, and releasing your API.
• RapidAPI - API marketplace to find, test and connect to all sorts of APIs.