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.
Fal.ai
Developer API platform for running image, video, and audio generation models (Flux, SDXL, Whisper, and more) at low latency. Popular as a serverless GPU layer for multimodal AI apps, with a clean Python/JS SDK and pay-per-use pricing.