A high-performance JSON Schema validator for JavaScript that uses dynamic code generation for V8 optimization.
JSEN is a JSON Schema validator library for JavaScript that emphasizes performance through dynamic code generation. It validates JSON objects against Draft 4 schemas and is designed to be fast by producing V8-optimized validator functions. The library supports both Node.js and browser environments with full schema compliance.
JavaScript developers who need fast, reliable JSON validation in performance-sensitive applications, such as API servers, data processing pipelines, or client-side form validation.
Developers choose JSEN for its speed advantage over other validators, full Draft 4 compliance, and flexibility with features like custom formats, external schema references, and detailed error reporting.
JSON-Schema validator built for speed
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Dynamically generates validator functions at runtime, which V8 can optimize for maximum performance, as evidenced by benchmarks comparing it to other validators like Ajv and z-schema.
Implements the complete JSON Schema Draft 4 specification with comprehensive validation, ensuring correctness for standard schemas without missing keywords.
Provides an array of validation errors with paths and keywords, supports custom error messages via invalidMessage and requiredMessage, and offers greedy mode to report multiple errors in one pass.
Allows custom format validators defined as regex strings, regex objects, or functions, enabling validation beyond built-in formats like URI and email.
Only supports JSON Schema Draft 4, making it unsuitable for newer drafts (e.g., Draft 7 or 2019-09) that include additional features and improvements, which limits modern adoption.
Does not automatically fetch remote schemas via HTTP; developers must manually download and provide them through the schemas option, adding complexity for distributed systems.
Relies on dynamic code generation (similar to eval), which can be blocked by strict Content Security Policies in browsers and poses potential security risks if schemas are untrusted.
Advanced features like custom formats, external schema references, and error customization require verbose setup in options, increasing initial learning curve and maintenance.