Mockzilla

A mock server generated from your OpenAPI spec

Point Mockzilla at an OpenAPI document and every path in it answers straight away. The data comes from your own schemas, so it respects types, formats, enums and required fields instead of being the same placeholder object everywhere.

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  • No handlers to write
  • Request validation
  • Several APIs, one URL
  • MIT licensed engine
GET /v1/customers/cus_9Fh2200
{
  "id": "cus_9Fh2",
  "email": "dana@example.com",
  "currency": "eur",
  "balance": 4210,
  "created": 1772841600,
  "delinquent": false
}
currency matched the enum, balance came back an integer, and nobody wrote a handler.

What is an OpenAPI mock server?

A server that reads an OpenAPI document and answers every path in it with data matching the schemas you declared. No handlers, no fixtures, and no second description of the API to keep in step with the first.

Mockzilla takes the spec as its only input. Upload it, or add the GitHub Action to the repository it lives in, and every endpoint starts answering on a stable URL your whole team can call.

Waiting for an API you can already describe

The spec is usually agreed long before the API is built. Until it exists the frontend is blocked, the integration tests have nothing to run against, and everyone writes throwaway fixtures that drift from the contract inside a week.

The mock is built from the spec itself, so it cannot drift. Change the spec and the mock changes with it. If one endpoint needs an exact response, write that one by hand and the rest keep generating.

Generated from your schemas

Every endpoint returns data that validates against its own response schema: types, formats, enums, required fields and nested objects.

Request validation

Incoming requests are checked against the spec, so a wrong body or a missing parameter fails at the mock instead of passing quietly.

Several APIs on one server

Each spec becomes a service with its own URL prefix, so your API and the third-party ones you depend on answer on the same host.

Questions

Do I have to write the responses myself?
No. The spec is the input, and every path in it answers without you writing anything.
Can I override one endpoint with a fixed response?
Yes. Put a JSON file at that path and it answers with exactly that body, while the rest of the spec keeps generating. The same works for paths your spec does not describe at all.
What if an endpoint needs real logic?
That is codegen mode. Mockzilla generates typed Go handlers from your spec, you write the behaviour you need, and you upload the compiled server. Anything you did not touch still answers from the spec.
How reliable is the generated data?
Response generation runs continuously against 2,215 public OpenAPI documents covering 98,464 endpoints, and every endpoint has to produce data that validates against its own schema.

Bring a spec. Get a mock server.

It costs nothing to start. Dedicated infrastructure when you need it.

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