How does is-my-json-valid compare to Ajv?

is-my-json-valid excels in raw performance with code generation, while Ajv offers broader JSONSchema compliance, including remote references and newer versions. Choose based on whether speed or feature completeness is more critical for your project.

How to add custom validation formats in is-my-json-valid?

Use the formats option when creating a validator, passing an object with custom keys mapped to regular expressions or functions, as demonstrated in the README's custom formats example for patterns like 'only-a'.

Does is-my-json-valid work with JSONSchema v6 or v7?

No, it specifically supports JSONSchema v4 with some limitations, and the README does not mention support for v6 or v7, so you might need another validator for newer schema versions.

Can I use is-my-json-valid to filter out extra properties in data?

Yes, it includes a filtering capability via validator.filter() that removes properties not defined in the schema, useful for data sanitization in APIs or ETL processes.

What are the main drawbacks of is-my-json-valid?

The key drawbacks are the lack of remote schema reference support and issues with unicode string length validation, which are explicitly noted in the README as not passing the full JSONSchema v4 test suite.

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is-my-json-valid

Q: Is is-my-json-valid really the fastest JSON validator?

Yes, according to the README, it ranks as the fastest in multiple benchmarks like json-schema-benchmark and cosmicreals.com due to its code generation approach that optimizes validation speed.

MITJavaScript

A high-performance JSONSchema validator that uses code generation for maximum validation speed.

GitHub

965 stars114 forks0 contributors

What is is-my-json-valid?

is-my-json-valid is a JSONSchema validator library that compiles JSON schemas into optimized JavaScript code for extremely fast validation. It solves the problem of slow schema validation in high-performance applications by generating efficient validation functions at runtime. The library supports most JSONSchema v4 features and provides detailed error reporting.

Target Audience

Developers building applications that require high-performance JSON validation, particularly those working with APIs, data processing pipelines, or any system where validation speed impacts overall performance.

Value Proposition

Developers choose is-my-json-valid because it consistently benchmarks as the fastest JSONSchema validator available, using code generation to achieve performance that significantly outperforms interpretation-based validators while maintaining full schema compliance.

Overview

A JSONSchema validator that uses code generation to be extremely fast

Use Cases

Best For

Validating API request/response payloads in high-traffic applications
Data processing pipelines where validation speed impacts throughput
Real-time form validation in Node.js applications
Ensuring data quality in ETL (Extract, Transform, Load) processes
Building validation middleware for Express.js or other Node.js frameworks
Type-safe validation with TypeScript integration

Not Ideal For

Applications requiring remote JSON schema references ($ref to external URLs), as remoteRefs are not supported.
Projects dealing with unicode-heavy data where accurate string length validation is essential, due to issues with surrogate pairs in maxLength/minLength.
Teams that prioritize extensive ecosystem support or plugins over raw performance, as the library focuses on core validation without many extras.
Environments where JavaScript code generation is restricted for security reasons, such as certain sandboxed or compliance-heavy contexts.

Pros & Cons

Pros

Blazing Fast Performance

Compiles schemas into optimized JavaScript code, making it consistently the fastest validator in benchmarks like json-schema-benchmark and cosmicreals.com.

Detailed Error Reporting

Supports verbose mode with error values and schema paths, providing actionable insights for debugging validation failures.

TypeScript Type Inference

Includes typings that construct interfaces from schemas, enabling type-safe validation and better developer experience in TypeScript projects.

Flexible Customization

Allows custom formats via regex or functions and supports external schema references with $ref, offering tailored validation rules.

Cons

Incomplete JSONSchema Compliance

Missing support for remoteRefs and has known bugs with unicode length validation, which may break strict schema adherence for some applications.

Imperfect TypeScript Support

The README admits typings are 'early on and not perfect,' potentially causing type issues in complex or edge-case schemas.

Code Generation Overhead

Initial schema compilation adds setup time, making it less efficient for one-off validations or dynamically changing schemas compared to interpreters.

Frequently Asked Questions

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