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This is a Java implementation of the JSON Schema Core Draft v4, v6, v7 and v2019-09 specification for JSON schema validation. In addition, it also works for OpenAPI 3.0 request/response validation with some configuration flags. The default JSON parser is the Jackson that is the most popular one. As it is a key component in our light-4j microservices framework to validate request/response against OpenAPI specification for light-rest-4j and RPC schema for light-hybrid-4j at runtime, performance is the most important aspect in the design.

Why this library


It is the fastest Java JSON Schema Validator as far as I know. Here is the testing result compare with the other two open-source implementations. It is about 32 times faster than the Fge and five times faster than the Everit.

fge: 7130ms

everit-org: 1168ms

networknt: 223ms

You can run the performance tests for three libraries from


It uses Jackson that is the most popular JSON parser in Java. If you are using Jackson parser already in your project, it is natural to choose this library over others for schema validation.

YAML Support

The library works with JSON and YAML on both schema definitions and input data.

OpenAPI Support

The OpenAPI 3.0 specification is using JSON schema to validate the request/response, but there are some differences. With a configuration file, you can enable the library to work with OpenAPI 3.0 validation.


Following the design principle of the Light Platform, this library has minimum dependencies to ensure there are no dependency conflicts when using it.

Here are the dependencies.





This library is very active with a lot of contributors. New features and bug fixes are handled quickly by the team members. Because it is an essential dependency of the light-4j framework in the same GitHub organization, it will be evolved and maintained along with the framework.


The library supports Java 8 and up. If you want to build from the source code, you need to install JDK 8 locally. To support multiple version of JDK, you can use SDKMAN


This package is available on Maven central.




dependencies {
    compile(group: "com.networknt", name: "json-schema-validator", version: "1.0.69");

For the latest version, please check the release page.

Quick Start



Specification Version

YAML Validation

Schema Mapping

Customized URIFetcher

Customized MetaSchema

Collector Context

JSON Schema Walkers and WalkListeners

ECMA-262 Regex

Custom Message

Known issues

I have just updated the test suites from the official website as the old ones were copied from another Java validator. Now there are several issues that need to be addressed. All of them are edge cases, in my opinion, but need to be investigated. As my old test suites were inherited from another Java JSON Schema Validator, I guess other Java Validator would have the same issues as these issues are in the Java language itself.




The light-rest-4j, light-graphql-4j and light-hybrid-4j use this library to validate the request and response based on the specifications. If you are using other frameworks like Spring Boot, you can use the OpenApiValidator, a generic OpenAPI 3.0 validator based on the OpenAPI 3.0 specification.

If you have a project using this library, please submit a PR to add your project below.


Thanks to the following people who have contributed to this project. If you are using this library, please consider to be a sponsor for one of the contributors.















For all contributors, please visit

If you are a contributor, please join the GitHub Sponsors and switch the link to your sponsors dashboard via a PR.


Individual Sponsors

Corporation Sponsors