Inferensys

Comparison

Gretel vs Mostly AI

A technical, data-driven comparison of Gretel's developer-first, open-source platform and Mostly AI's enterprise-focused synthetic data engine. We evaluate core differentiators in API design, privacy guarantees, multi-relational synthesis, and suitability for regulated industries like banking and healthcare.
Developer demonstrating multi-agent tool use, agent tool selection interface on laptop, casual tech demo moment.
THE ANALYSIS

Introduction

A data-driven comparison of Gretel and Mostly AI, two leading platforms for generating privacy-safe synthetic data in regulated industries.

Gretel excels at developer-centric flexibility and open-source innovation, offering a cloud-native API and SDKs that integrate seamlessly into modern MLOps pipelines. Its core strength lies in providing granular control over the generation process, supporting a wide range of data types from tabular to time-series, and enabling custom model tuning. For example, Gretel's Navigator and Synthetic Data Vault (SDV) integrations allow teams to generate and evaluate synthetic data with specific utility metrics, making it ideal for agile teams building custom AI training datasets or testing environments. This approach is particularly effective for organizations that prioritize integration speed and need to support diverse, complex data schemas as part of their broader LLMOps and Observability Tools strategy.

Mostly AI takes a different, enterprise-focused approach by prioritizing automated, high-fidelity synthesis with robust out-of-the-box privacy guarantees. Its strategy centers on delivering production-ready synthetic datasets that preserve complex statistical properties and multi-table relationships with minimal configuration. This results in a trade-off: exceptional ease-of-use and consistency for standard enterprise schemas, but potentially less flexibility for highly custom or novel data structures. Mostly AI's strength is its proven ability to generate data that passes rigorous fidelity scoring tests, a critical factor for financial institutions under model risk management (MRM) frameworks and for healthcare applications requiring defensible de-identification under HIPAA.

The key trade-off: If your priority is developer agility, open-source tooling, and custom pipeline integration for varied data types, choose Gretel. It is the superior choice for engineering-led teams who need to embed synthetic data generation into a broader AI development lifecycle. If you prioritize turnkey enterprise deployment, automated high-fidelity output, and strong, auditable privacy guarantees for regulated use cases in banking or healthcare, choose Mostly AI. Your decision should also consider whether you need a platform specializing in multi-relational synthesis (a strength of both, but a core focus for Mostly AI) or if you are evaluating the broader category of Synthetic Data Platform vs Custom In-House Solution.

HEAD-TO-HEAD COMPARISON

Gretel vs Mostly AI: Feature Comparison

Direct comparison of key metrics and features for synthetic data generation platforms, focusing on regulated industry use cases.

Metric / FeatureGretelMostly AI

Core Architecture

Open-source & cloud-native APIs

Enterprise-focused, high-fidelity engine

Primary Deployment

Cloud-first (AWS, GCP, Azure)

Cloud & on-premises/private cloud

Multi-Relational Synthesis

Built-in Differential Privacy

Fidelity Scoring (Utility Metrics)

TSTR, Kolmogorov-Smirnov

Proprietary high-fidelity metrics

API-First Design

Referential Integrity Guarantees

For linked tables

Strong, automated for complex schemas

Synthetic Data for Time Series

GRETEL VS MOSTLY AI

TL;DR Summary: Key Differentiators

A quick scan of core strengths and trade-offs for two leading synthetic data platforms, based on API flexibility, privacy guarantees, and enterprise readiness.

02

Gretel: Multi-Modal & Hybrid Privacy

Flexible privacy stack: Combines Differential Privacy (DP), synthetic generation, and transform models for a hybrid approach. This allows teams to tune the privacy-utility trade-off based on the dataset and use case, providing defensible privacy for diverse data types beyond tabular, including text and time-series.

04

Mostly AI: Automated Multi-Relational Synthesis

Preserves complex referential integrity: Automatically models and synthesizes the relationships between multiple database tables (e.g., Customer -> Account -> Transaction). This is critical for testing enterprise applications and generating realistic, connected datasets without manual schema definition, a key differentiator for financial services use cases. For more on multi-relational synthesis, see our comparison on Row-level vs Multi-relational Synthesis.

05

Choose Gretel For...

Developer-centric workflows and hybrid privacy control.

  • Use Case: Embedding synthetic data into custom ML pipelines, rapid experimentation with different models (GANs, VAEs, LLMs).
  • Regulatory Focus: Scenarios requiring tunable, mathematically rigorous privacy guarantees like Differential Privacy (DP).
  • Trade-off: Accepts more configuration overhead for greater flexibility and control over the generation stack.
06

Choose Mostly AI For...

Out-of-the-box enterprise fidelity and automation.

  • Use Case: Generating high-quality, connected datasets for model validation, application testing, and analytics in banking/healthcare.
  • Regulatory Focus: Audits requiring automated, report-driven proof of statistical utility and privacy.
  • Trade-off: Prioritizes ease-of-use and automated quality over deep, low-level model customization. For a deeper dive into platform trade-offs, explore our analysis of Commercial SDG Platforms vs Custom In-House Solutions.
CHOOSE YOUR PRIORITY

When to Choose Gretel vs Mostly AI

Gretel for Developers

Verdict: The superior choice for agile, API-first development and open-source integration. Strengths: Gretel is built for developers with a comprehensive Python SDK, a rich open-source ecosystem (including its own libraries), and a cloud-native API designed for CI/CD pipelines. It offers granular control over the synthesis process, allowing for custom model tuning and integration with tools like MLflow and Databricks. The platform excels in generating data for RAG pipelines and agentic workflows where programmatic, on-demand data generation is required. Its developer experience prioritizes flexibility and automation. Key Metrics: Lower time-to-first-synthetic-record via API, extensive documentation and code examples, support for custom Differential Privacy (DP) and Generative Adversarial Network (GAN) configurations.

Mostly AI for Developers

Verdict: A robust enterprise platform, but less focused on developer-centric agility. Strengths: Mostly AI provides a powerful, managed service with a strong REST API. However, its primary interface is a sophisticated web UI aimed at data scientists and business users. It automates much of the model selection and hyperparameter tuning, which reduces developer overhead but also limits deep technical customization compared to Gretel. It's ideal for teams that prioritize a managed, high-fidelity output over granular engineering control. For more on API-driven data generation, see our guide on Synthetic Data Platform vs Custom In-House Solution.

THE ANALYSIS

Verdict and Final Recommendation

A final, data-driven comparison to help you choose the right synthetic data platform for your regulated industry needs.

Gretel excels at developer agility and open-source flexibility because of its API-first, cloud-native architecture. For example, its open-source tools like Gretel Synthetics offer transparent, customizable models, and its cloud service provides a reported 99.9% uptime SLA, making it ideal for teams needing to iterate quickly and integrate synthetic data generation into CI/CD pipelines. Its strength lies in enabling rapid prototyping and offering fine-grained control over the privacy-utility trade-off, which is critical for research and development in dynamic environments.

Mostly AI takes a different approach by prioritizing enterprise-grade, automated high-fidelity synthesis. This results in superior out-of-the-box statistical accuracy for complex, multi-relational datasets—a key metric for banking and healthcare clients. For instance, its platform consistently achieves high scores on fidelity metrics like Kolmogorov-Smirnov tests while maintaining strong privacy guarantees, reducing the need for extensive data science tuning. The trade-off is less developer-centric configurability in favor of a polished, compliance-ready product.

The key trade-off: If your priority is developer control, open-source integration, and agile development for a variety of data types, choose Gretel. It is the superior choice for engineering teams building custom data pipelines. If you prioritize production-ready, high-fidelity data for complex enterprise schemas with minimal setup and maximum compliance defensibility, choose Mostly AI. It is the stronger option for regulated industries like banking and insurance that require audit-ready synthetic data for model training and testing. For further reading on enterprise integration, see our comparison of K2view vs Gretel, and for a look at specialized financial services tools, explore Mostly AI vs Hazy.

Prasad Kumkar

About the author

Prasad Kumkar

CEO & MD, Inference Systems

Prasad Kumkar is the CEO & MD of Inference Systems and writes about AI systems architecture, LLM infrastructure, model serving, evaluation, and production deployment. Over 5+ years, he has worked across computer vision models, L5 autonomous vehicle systems, and LLM research, with a focus on taking complex AI ideas into real-world engineering systems.

His work and writing cover AI systems, large language models, AI agents, multimodal systems, autonomous systems, inference optimization, RAG, evaluation, and production AI engineering.