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Gretel.ai vs Mock Service Worker

Feature checklists rarely decide anything. What decides it is the pricing metric, who has to write the tests, and which limitation you can live with.

Gretel.aiTest Data & Mocks
Mock Service WorkerTest Data & Mocks

Entry price

Quote on request

Quote only

Free and open source

Open source

What drives the bill

The metric that actually scales your invoice.

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.

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

Free tier

Everything, self-hosted

Open source

MIT

Self-hostable

No-code authoring

Languages

PythonCodeless
JavaScriptTypeScript

Platforms

API
WebAPI

Fits teams

Enterprise
Solo / side projectStartupScale-up / mid-marketEnterprise

Adoption

Emerging

NVIDIA (formerly Gretel) · since 2019

Category standard

OSS community · since 2020

Strengths

  • 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.
  • One set of handlers reused across unit, component, E2E and local development.
  • Application code is completely unaware it is being mocked — no test-only branches.
  • Supports REST and GraphQL with the same model.

Limitations

  • 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.
  • JavaScript ecosystem only.
  • Service Worker registration adds a setup step and occasional caching confusion.
  • Handlers can drift from the real API without contract verification.

Best for

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

Front-end teams that want one mocking approach across every kind of test.

Full review
Full review

Pricing last reviewed August 2026 and is indicative only — confirm on each vendor’s own page.