Blaze

The ultra high-performance JSON Schema validator for C++ with support for JSON Schema Draft 4, Draft 6, Draft 7, 2019-09, and 2020-12.

Want to use Blaze without writing C++? Check out our JSON Schema CLI, which is powered by Blaze, and offers advanced functionality like validate --trace for debugging schema evaluation.

Benchmark

The 2025 paper Blaze: Compiling JSON Schema for 10x Faster Validation presents a reproducible benchmark comparing Blaze against a number of popular JSON Schema validators, concluding that Blaze is on average at least 10x faster than competitors given a large set of representative schemas and instances.

Features

• Performance: Blaze compiles JSON Schema into a lower-level intermediate language for ultra fast evaluation. It can achieve schema validation in the nano-second range, making it a perfect fit for low-latency gateways and validation of large datasets

• Compliance: Blaze achieves a 100% compliance score in the official Bowtie benchmark, while popular validators like AJV only achieve an average 85% compliance. It also supports the Standard Output format (Flag, and Basic). Furthermore, Blaze is built and maintained by a JSON Schema TSC member

• Extensibility: Blaze supports the implementation of custom vocabularies of arbitrary complexity, and the ability to setup custom resolution of external schemas from arbitrary sources, like from HTTP, filesystem, databases, etc

• Annotations: Blaze is one of the few implementations that fully supports annotation extraction during evaluation to augment instances with semantic information, making it a great fit for data science scenarios. Blaze also adheres to the annotations official test suite

• Numerics: Blaze supports high precision decimals. For performance reasons, these representations are only used if the numbers fail to be parsed at the JSON level using the 64-bit signed and IEEE 764 double precision representations or (as a heuristic) if the numbers explicitly opt-in to exponent scientific notation

Example

Blaze is designed to be easy to use, while at the same time providing extensive hooks for supporting custom vocabularies, resolving external schemas, and more.

// (1) Get a JSON Schema
const auto schema{sourcemeta::core::parse(R"JSON({
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "string"
})JSON")};

// (2) Compile the JSON Schema into an optimised representation
const auto compiled_schema{sourcemeta::blaze::compile(
  schema,

  // These options allow you tweak how Blaze works,
  // the JSON Schema vocabularies it understands,
  // and how to resolve references to external schemas
  sourcemeta::core::schema_official_walker,
  sourcemeta::core::schema_official_resolver,
  sourcemeta::blaze::default_schema_compiler,

  // Fast validation means getting to a boolean result
  // as fast as possible. Check out the documentation
  // for how to get detailed error information and/or
  // collect JSON Schema annotations
  sourcemeta::blaze::Mode::FastValidation)};

// (3) Get a JSON instance
const sourcemeta::core::JSON instance{"Hello Blaze!"};

// (4) Validate the instance against the schema
sourcemeta::blaze::Evaluator evaluator;
const auto result{evaluator.validate(compiled_schema, instance)};
if (result) {
  std::cout << "Success!\n";
}

Documentation

Refer to the project website for documentation: https://blaze.sourcemeta.com.

Roadmap

• Support running the validator on simdjson
• Provide bindings to higher-level programming languages (Node.js, Go, etc)

Contributors

Blaze was designed and developed by a team of passionate JSON Schema developers and researchers.