# What users say
In the past 6 years of working on the JSON Schema Specification itself, Ajv stands out as the implementation of choice. It is very well documented and provides a rich API for extending JSON Schema which many thousands of people use in production today. A huge effort was put into testing, with many tests now forming part of the official test suite.
I've personally used Ajv in production to validate requests for a federated undiagnosed genetic disease program that has lead to new scientific discoveries and literally changed lives.
Ajv development can inform the future tooling and specification changes. There's no doubt that Ajv is partly responsible for the ubiquity and success of JSON Schema.
Ben Hutton (opens new window), JSON Schema Specification Lead
ESLint (opens new window) has used Ajv for validating our complex configurations. Ajv has proven to be reliable over the years we’ve been using it and ESLint is proud to sponsor Ajv’s continued development.
Nicholas C. Zakas (opens new window), ESLint creator and TSC member
I always thought that built-in data validation is a key feature of any web framework. We decided to leverage JSON Schema in Fastify (opens new window), and Ajv fits our needs wonderfully: it’s fast, stable and well maintained.
Ajv has become a centerpiece of all data-validation logic in my open-source projects and businesses. It is spec-compliant, extensible, fast and has amazing support.