The OpenAI API gives developers programmatic access to all of OpenAI's models. Key endpoints: Responses API (the modern conversation interface, replacing the older chat completions endpoint), embeddings (vector search), DALL-E (image generation), Whisper (speech-to-text), TTS (text-to-speech), Sora (video). Pricing is per-token for LLMs, per-image for DALL-E, per-second for audio/video. Major features: structured outputs (JSON schema-validated returns), function calling (tool use), prompt caching (50% discount on cached prefixes), assistants/threads (managed conversation state). The API serves the majority of commercial LLM workloads in 2026, even as Anthropic and Google chip away.
GLOSSARY
What is OpenAI API?
Programmatic access to OpenAI's models (GPT-5, o-series, embeddings, DALL-E, Whisper, Sora). The most widely-used commercial LLM API.
RELATED TERMS
LLM (Large Language Model)
An AI system trained on massive text datasets to predict and generate human-like text — the technology behind ChatGPT, Claude, Gemini, and most modern AI chatbots.
ChatGPT
OpenAI's flagship chatbot, launched November 2022. The product that brought conversational AI to the mainstream — now serving 200M+ weekly active users.
Anthropic API
Programmatic access to Anthropic's Claude models with prompt caching, extended thinking, computer use, file analysis, and the Agent SDK.
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