Back to the registry
Mock any API in the registry
Build against an API before you have credentials, before it is live, or when the real one is rate limited — from the same specification the registry already serves.
Step 1
Open any API
Pick a listing from the registry — any of them, mirrored or published by an organisation on Spec0.
Step 2
Create the mock
Its page carries a create-mock action. Creating an account is part of that same step, so nothing is lost if you do not have one yet.
Step 3
Point your code at the URL
You get a base URL that answers every operation in the spec, with responses shaped by the schemas the API actually declares.
What you get
- Every operation in the spec, answering immediately
- Responses built from the spec's own schemas and examples
- Request validation, so a malformed call fails like the real API would
- Variants, to make an endpoint return the error path on demand
- Request logs, to see exactly what your code sent
- Its own MCP server, so an agent can drive the mock while it writes the client
Start from an API
The create-mock action is on each listing, where there is no doubt which spec you meant.