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Overview

Onefast API gives you GPT, Claude, Gemini, DeepSeek, Qwen and other leading models with one API key, compatible with the OpenAI, Anthropic and Gemini native protocols.

What you can do

  • One key for every model: text, reasoning, images, video, speech and embeddings, with unified billing and a single bill.
  • Native protocols: with the OpenAI SDK, Anthropic SDK or Google GenAI SDK, change only base_url and the key — the rest of your code stays the same.
  • Ready for coding tools: Claude Code, Codex CLI, Gemini CLI, Cherry Studio, Cursor and more.
  • Choose routes by group: the same model can be called through different groups (routes), each with its own balance of price and stability. See Groups & billing.

Base URL

All endpoints share the same root URL:

Base URL

https://api.onefast.ai
Protocol Endpoint Best for
OpenAI-compatible https://api.onefast.ai/v1/chat/completions, /v1/responses, etc. Most SDKs and tools; any model
Anthropic native https://api.onefast.ai/v1/messages Claude models, Claude Code
Gemini native https://api.onefast.ai/v1beta/models/{model}:generateContent Gemini models, Gemini CLI
Volcengine Ark-compatible https://api.onefast.ai/api/v3/contents/generations/tasks Seedance video

With the OpenAI SDK, base_url must include /v1. With the Anthropic SDK, Claude Code or Gemini CLI, do not include /v1 — just use the root URL.

Get started in three steps

  1. Sign up and log in to the console, then create an API key on the "API Keys" page and select the groups to use.
  2. Send your first request with the Quickstart.
  3. Browse available models and live prices in the model catalog.

Where to go next

I want to… Go to
Get a first request working in 5 minutes Quickstart
Understand keys and groups Authentication, Groups & billing
Call GPT / Claude / Gemini Chat completions, Claude Messages, Gemini native
Generate images, video or speech Image generation, Video generation, Audio & embeddings
Use it in Claude Code / Codex Client integrations
Look up fields and test live API reference
Troubleshoot errors Errors, FAQ