StepFun Open Platform (阶跃星辰开放平台) is the developer service of StepFun (阶跃星辰), a Shanghai company founded in April 2023 that trains its own large models. A large language model (LLM) is a neural network trained on large amounts of text to generate text.
A program calls the API (an interface used by other programs over the internet) with an API key. The platform's code example uses the OpenAI Python library with the base address set to api.stepfun.com/v1. The models include the flagship Step 5 Preview, the faster Step 3.7 Flash and Step 3.5 Flash, a vision model that reads images, and the StepAudio 3 family for real-time voice conversation, speech synthesis (text to speech), speech recognition (speech to text) and music generation. A browser Studio tests models without code, and the Builder Program gives independent developers and startups credits and technical support.
It is a hosted service. API calls are billed by use in Chinese yuan: per million tokens (short pieces of text) for text models, and per character or per hour of audio for some voice models. A monthly subscription, Step Plan, gives a fixed monthly credit instead.