Mockoon vs Gretel.ai

From $100 per month (Team, billed annually, up to 5 members)

Quote on request

Free locally and forever; the paid cloud tier adds hosted mocks and team sync. Team covers 5 members, 3 cloud-deployed mocks and 100k calls a month, with Enterprise on a quote. Work emails get a 14-day trial, others 7 days with a card.

The old credit-based self-serve tier is gone. The successor microservices are licensed through NVIDIA AI Enterprise; NeMo Data Designer can be tried on build.nvidia.com.

The desktop app and CLI are free and open source.

Widely used

Mockoon · since 2017

Emerging

NVIDIA (formerly Gretel) · 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, now via DP-SGD in NeMo Safe Synthesizer.
• Synthetic data preserves statistical relationships useful for analytics and model training.
• Backed by NVIDIA's platform investment rather than a single startup's runway.

• 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.

• No longer buyable as Gretel — you are procuring NVIDIA AI Enterprise, which is far heavier than the old self-serve signup.
• Model training adds time and cost compared to rule-based masking.
• Safe Synthesizer trains on a real dataset, so it does not help with greenfield data that does not exist yet.

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

Regulated enterprises already standardising on NVIDIA AI Enterprise. Teams that wanted Gretel's self-serve tier should look at Tonic or Neosync instead.