API

An API (Application Programming Interface) is a contract between two software systems that defines how they communicate. When applied to AI, APIs allow any developer to integrate powerful AI capabilities — text generation, image recognition, speech-to-text — into their own applications by sending requests to a remote AI service and receiving structured responses. This is how most organizations access frontier AI models: rather than training their own models, they send prompts to OpenAI's API, Anthropic's API, or Google's API and receive AI-generated outputs in return.

The AI API model has transformed how AI is deployed. Companies like OpenAI, Anthropic, Google, and others host their models on powerful server clusters and expose them through simple HTTP endpoints. A developer sends a request containing a prompt (and optionally parameters like temperature or max tokens) and receives the model's response. This cloud-based approach means developers can access models costing hundreds of millions of dollars to train without owning specialized hardware. Pricing is typically per-token, allowing costs to scale with usage.

APIs are the primary mechanism through which AI capabilities reach end users. Every time you use an app with AI features — smart compose in email, AI-powered search, chatbot support, photo editing with generative fill — there is likely an API call to an AI model behind the scenes. Understanding APIs is therefore essential for anyone building AI-powered products. Beyond model APIs, the AI ecosystem includes APIs for vector databases, speech recognition, computer vision, and thousands of specialized services that can be composed to build complex AI applications.