Mockoon vs Gretel.ai

From $9 per user/month (indicative, Cloud)

Free tier available

Free locally; the paid cloud tier adds hosted mocks and team sync.

Consumption-based on generated records; enterprise agreements available.

The desktop app and CLI are free and open source.

Free tier with a monthly credit allowance.

Widely used

Mockoon · since 2017

Emerging

Gretel (NVIDIA) · since 2019

• Genuinely a minute from download to a working mock API.
• Dynamic templating with faker-style helpers produces realistic responses.
• Proxy mode mocks only the routes you need and passes the rest through.

• Formal differential-privacy guarantees rather than best-effort masking.
• Synthetic data preserves statistical relationships useful for analytics and model training.
• Privacy and quality scores make the trade-off explicit.

• Desktop-first; sharing mocks across a team needs the paid cloud or a committed config file.
• HTTP only.
• Less suited to complex stateful behaviour than WireMock.

• Model training adds time and cost compared to rule-based masking.
• Overkill when simple anonymisation would satisfy the requirement.
• NVIDIA acquisition changes the strategic outlook.

Front-end developers unblocking themselves while a backend is still being built.

Regulated organisations that need shareable data with defensible privacy properties.