Prism vs Mockaroo

Free and open source

From $60 per year (indicative, Silver)

Free and open source. You pay in engineering time and CI minutes.

Cheap for what it does; higher tiers raise row limits and add API quota.

Everything, self-hosted

Free for up to 1,000 rows per download and a limited number of saved schemas.

Established

Stoplight (SmartBear) · since 2017

Established

Mockaroo LLC · since 2014

• The mock is generated from the spec, so it cannot silently diverge from the contract.
• Validation proxy mode checks that a real implementation matches its own spec.
• Zero configuration beyond having an OpenAPI file.

• No code required — an analyst or tester can design a dataset themselves.
• Very large library of realistic field types including regional formats.
• Formula fields allow simple business rules between columns.

• Useless without an accurate OpenAPI document.
• Limited stateful behaviour — it is spec-driven, not scenario-driven.
• Generated example data is uninteresting unless examples are in the spec.

• Referential integrity across related tables is limited.
• Free-tier row limits are low for realistic volume testing.
• Data is generated on a third-party service, which needs a privacy check for schema sensitivity.

Design-first API teams who want mocks that are provably in sync with the contract.

Quickly producing a realistic dataset for a demo, a load test or a new environment.