OpenAPI → coherent mock API

Mock APIs from your OpenAPI spec, with data that
actually connects.

Mocksmith reads your spec, infers how your entities relate, and generates one coherent dataset. The same customerId resolves across /orders, /customers, and /invoices — realistic values, no random UUIDs, no dead foreign keys.

Your spec is the contract. Mocksmith makes sure every mock honors it — built for contract-first teams.

Paste a spec, get a hosted mock URL. Live in under 5 minutes.

Other mock tools fake each endpoint. The data falls apart the moment it connects.

Generate a mock with Prism, Mockoon, or Postman and GET /orders/42 hands back a customerId that exists nowhere. Click through and you get a 404. The data is random per endpoint, so nothing lines up.

Other mock tools

GET /orders/42
{
  "id": 42,
  "customerId": "9f3b1c7e-44a2-4f08-bd31",
  "total": 129.00
}

GET /customers/9f3b1c7e-44a2-4f08-bd31
→ 404 Not Found

The customerId points at a customer that doesn't exist. Your flow breaks the moment it follows the link.

Mocksmith

GET /orders/42
{
  "id": 42,
  "customerId": 318,
  "total": 129.00
}

GET /customers/318
{
  "id": 318,
  "name": "Alice Tan",
  "email": "alice.tan@example.com"
}

customerId: 318 resolves to the same realistic customer — everywhere it appears across your API.

Mocksmith infers the foreign keys from your spec and generates one coherent dataset — the same entity is identical everywhere.

How it works

1Paste your OpenAPI spec — URL or file

2Mocksmith infers your entities and how they relate

3Copy your hosted URL — every endpoint returns connected data

Why Mocksmith, not another endpoint mocker

Every tool can stand up endpoints. Only Mocksmith makes the data between them coherent.

Capability	Mockoon	Prism	Postman	WireMock	Mocksmith
Generate a mock from an OpenAPI spec
Realistic field values by meaning
Cross-endpoint data coherence (foreign keys resolve)
Auto-infers entity relationships from the spec
Hosted, zero local setup
No manual example authoring

As of 2026, based on each tool's documented default behavior. “Partial” = possible, but manual or limited.

See the full breakdown vs Postman Mock, Prism & Mockoon →

Free to join — no credit card required.

What's in the MVP

Instant mock servers

MVP

Turn any OpenAPI spec into live, hosted endpoints. No backend, no config.

Coherent relational data

MVP

Foreign keys resolve across endpoints. The same entity is identical everywhere it appears.

Realistic values by field meaning

MVP

Emails look like emails, prices like prices — inferred from each field's role, not random noise.

Reusable scenarios

Planned

Save and replay curated datasets and edge cases. Coming after the core release.

Get early access to coherent mock APIs.

Mocksmith is in early access. It's for developers tired of mock data that lies — random IDs, broken relationships, fixtures that drift.

Leave your email and we'll reach out as we open up access.

Get early access

We'll email you when your spot opens — feature requests welcome.

Free to join — no credit card required.

Built by engineers tired of mock data that lies.

Random IDs, broken relationships, fixtures that drift from the spec — we've shipped around all of it.

Mocksmith is the tool we wanted: paste a spec, get mock data that behaves like a real backend.

Mock APIs from your OpenAPI spec, with data thatactually connects.