jsonschema

A high-performance JSON Schema validator for Rust.

use serde_json::json;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let schema = json!({"maxLength": 5});
    let instance = json!("foo");

    // One-off validation
    assert!(jsonschema::is_valid(&schema, &instance));
    assert!(jsonschema::validate(&schema, &instance).is_ok());

    // Build & reuse (faster)
    let validator = jsonschema::validator_for(&schema)?;

    // Fail on first error
    assert!(validator.validate(&instance).is_ok());

    // Iterate over errors
    for error in validator.iter_errors(&instance) {
        eprintln!("Error: {error}");
        eprintln!("Location: {}", error.instance_path());
    }

    // Boolean result
    assert!(validator.is_valid(&instance));

    // Structured output (JSON Schema Output v1)
    let evaluation = validator.evaluate(&instance);
    for annotation in evaluation.iter_annotations() {
        eprintln!(
            "Annotation at {}: {:?}",
            annotation.schema_location,
            annotation.annotations.value()
        );
    }

    // Generated validators are significantly faster than runtime validators,
    // so prefer them when the schema is known at build time.
    // Requires the `macros` feature.
    // Inline schema, or `path = "schema.json"` to load from a file
    #[jsonschema::validator(schema = r#"{"maxLength": 5}"#)]
    struct Short;

    assert!(Short::is_valid(&instance));
    Short::validate(&instance)?;

    Ok(())
}

You also can use it from the command line via the jsonschema-cli crate.

$ jsonschema-cli schema.json -i instance.json

See more usage examples in the documentation.

⚠️ Upgrading from older versions? Check our Migration Guide for key changes.

Playground

If you'd like to try jsonschema, you can check the WebAssembly-powered playground to see the results instantly.

Highlights

• 📚 Full support for popular JSON Schema drafts
• 🔧 Custom keywords and format validators
• 🌐 Blocking & non-blocking remote reference fetching (network/file)
• 🎨 Structured Output v1 reports (flag/list/hierarchical)
• ✨ Meta-schema validation for schema documents, including custom metaschemas
• 🧮 Experimental schema canonicalization
• 🧩 Validation of custom in-memory JSON representations
• 🔗 Bindings for Python and Ruby
• 🚀 WebAssembly support
• 💻 Command Line Interface

Supported drafts

The following drafts are supported:

• 
• 
• 
• 
• 

You can check the current status on the Bowtie Report.

Notable Users

• Tauri: Config validation
• Apollo Router: Config file validation
• qsv: CSV record validation with custom keyword & format validator

Performance

jsonschema outperforms other Rust JSON Schema validators in most scenarios. The numbers below are for the runtime validator, which compiles a schema into a reusable Validator:

• Up to 75-645x faster than valico and jsonschema_valid for complex schemas
• Generally 2-52x faster than boon, and >5000x faster for recursive schemas

When the schema is known at build time, the #[jsonschema::validator] macro (macros feature) generates a specialized validator at compile time. This avoids schema compilation at runtime and validates roughly 3-13x faster than the runtime validator across our benchmark schemas.

For detailed benchmarks, see our full performance comparison.

Minimum Supported Rust Version (MSRV)

This crate requires Rust 1.85.0 or later.

TLS Configuration

By default, jsonschema uses aws-lc-rs as the TLS cryptography provider, which is the default one in reqwest.

Using Ring Instead

You can opt into using ring as the TLS provider:

[dependencies]
jsonschema = {
    version = "0.42",
    default-features = false,
    features = ["resolve-http", "resolve-file", "tls-ring"]
}

NOTE: If both tls-aws-lc-rs and tls-ring features are enabled, aws-lc-rs takes precedence.

Acknowledgements

This library draws API design inspiration from the Python jsonschema package. We're grateful to the Python jsonschema maintainers and contributors for their pioneering work in JSON Schema validation.

Support

If you have questions, need help, or want to suggest improvements, please use GitHub Discussions.

Sponsorship

If you find jsonschema useful, please consider sponsoring its development.

Contributing

We welcome contributions! Here's how you can help:

• Share your use cases
• Implement missing keywords
• Fix failing test cases from the JSON Schema test suite

See CONTRIBUTING.md for more details.

License

Licensed under MIT License.