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AI · openapi

OpenAI API Mock Server

Chat, embeddings, files, assistants

Develop against the OpenAI API without spending tokens. Carbon serves chat completions, embeddings, files, and assistants locally with deterministic responses — perfect for CI, benchmarks, and offline demos.

Quickstart

npx carbon-api emulate --catalog openai

Runs on http://localhost:8787 by default. No account, no signup.

Try it

Real HTTP against the local replica.

Create a chat.completion

curl -X POST http://localhost:8787/chat.completions \
  -H 'content-type: application/json' \
  -d '{"name":"example"}'

List them back (state persists)

curl http://localhost:8787/chat.completions

What's covered

Carbon compiles the entire spec — these are just the resources most integrations reach for first.

  • chat.completions
  • embeddings
  • files
  • assistants

Under the hood

Everything Carbon gives you comes with this emulator — for free.

  • · Stateful CRUD — writes persist across requests.
  • · Snapshots — freeze and restore the whole world with one command.
  • · Chaos presets — inject latency, 5xx, and network errors on demand.
  • · Deterministic — the same requests produce the same responses in CI.
OpenAI docs →All emulators