Anthropic API
API access to Claude model family including Claude 3.5 Sonnet, Haiku, and Opus. Excels at coding, analysis, long-context tasks, and safety-critical applications.
OpenAI API
API access to GPT-5, GPT-5.5, o3/o4 reasoning models, and the Responses API; plus embeddings, image, audio, and Realtime endpoints. The most widely deployed LLM API in production.