JSON Schema Generator & Validator
Generate JSON Schema from JSON samples automatically, and validate JSON documents against schemas. Auto-detect types, required fields, and constraints.
Validation Result
About JSON Schema Generator & Validator
Our free online JSON Schema Generator & Validator is a comprehensive tool for working with JSON Schema, the standard for describing the structure and constraints of JSON data. JSON Schema provides a contract for what JSON data is required for a given application and how to interact with it, making it essential for API development, data validation, and documentation.
The Schema Generator analyzes your JSON sample data and automatically creates a JSON Schema document. It intelligently detects data types (string, number, boolean, array, object), identifies required fields, recognizes common patterns (email addresses, URLs, dates), infers enum values from repeated data, and calculates minimum/maximum constraints for numeric values. You can configure the generation options to include example values, adjust the schema draft version, and control how aggressively patterns are detected.
The Schema Validator takes a JSON document and a JSON Schema, then validates whether the JSON conforms to the schema's rules. It checks required fields, property types, array item counts, string patterns, numeric ranges, and nested object structures. Validation errors are reported with clear messages indicating exactly which field failed validation and why, along with the JSON path to the problematic value.
JSON Schema is widely used in modern web development: OpenAPI/Swagger specifications use it for request/response validation, form builders use it to generate UI components, databases use it for data integrity checks, and configuration management tools use it to validate settings files. This tool supports Draft 04, Draft 07, and Draft 2020-12 schema versions.
Related JSON Tools
Features
Auto Schema Generation
Generate complete JSON Schema from sample JSON data with one click. Type inference and constraint detection included.
Schema Validation
Validate JSON documents against schemas. Get detailed error messages with JSON paths for easy debugging.
Pattern Detection
Automatically detect email, URL, date, and date-time patterns and add format constraints to the schema.
Enum Inference
Detect repeated values and suggest enum constraints for fields with a small set of possible values.
Multiple Draft Versions
Support for Draft 04, Draft 07, and Draft 2020-12 schema specifications with appropriate $schema URIs.
Nested Structure Support
Handle deeply nested objects and arrays with proper schema generation and validation at every level.
Copy & Download
One-click copy schema to clipboard or download as a .json file for use in your projects.
Statistics
View input/output character counts, property count, and schema depth for quick overview.
Privacy First
All processing happens in your browser. Your data never leaves your device, ensuring complete security.
How to Use
Choose a Mode
Select "Schema Generator" to create schema from JSON, or "Schema Validator" to validate JSON against a schema.
Input Your Data
For Generator: paste JSON sample. For Validator: paste JSON in left editor and schema in right editor. Click "Sample" for examples.
Configure Options
Set schema draft version, enable/disable pattern detection, required fields inference, and example inclusion.
Generate or Validate
Click "Generate Schema" or "Validate JSON". Review the generated schema or validation results with detailed error messages.
Frequently Asked Questions
What is JSON Schema?
JSON Schema is a vocabulary that allows you to annotate and validate JSON documents. It defines the structure, data types, required fields, and constraints for JSON data. JSON Schema is used for data validation, documentation, API testing, form generation, and configuration management. It is a JSON-based format that itself is valid JSON, making it easy to work with in any programming language.
How does the Schema Generator work?
The generator analyzes your JSON sample and infers the schema by: (1) Detecting data types for each value (string, number, boolean, array, object, null). (2) Identifying which fields are present and marking them as required. (3) Recognizing common string patterns like email addresses, URLs, and dates to add format constraints. (4) Calculating min/max for numeric values. (5) Detecting repeated string values to suggest enums. (6) Recursively processing nested objects and arrays.
What schema draft versions are supported?
This tool supports three major JSON Schema draft versions: Draft 04 (the oldest widely used version), Draft 07 (adds if/then/else, const, and content encoding), and Draft 2020-12 (the latest version with $defs, unevaluatedProperties, and improved vocabulary system). The appropriate $schema URI is automatically set based on your selection.
What patterns can be auto-detected?
The generator can automatically detect: email addresses (format: "email"), URLs (format: "uri"), dates in YYYY-MM-DD format (format: "date"), ISO 8601 date-time strings (format: "date-time"), and UUIDs (pattern constraint). Pattern detection can be enabled or disabled in the options.
How accurate is the auto-generated schema?
The auto-generated schema is a good starting point based on the sample data you provide. However, it may not capture all constraints (e.g., it cannot know the maximum length of a string from a single sample). It's recommended to review and refine the generated schema, adding constraints like maxLength, minLength, pattern, minimum, maximum, and enum values that reflect your actual business rules.
How does the Schema Validator work?
The validator checks the JSON document against the schema rules: required fields must be present, property types must match, arrays must have the correct item types, strings must match format/pattern constraints, numbers must be within min/max ranges, and nested objects must conform to their sub-schemas. Errors are reported with the JSON path (e.g., $.users[0].email) and a clear description of what failed.
Is this JSON Schema tool free?
Yes, it is completely free to use with no registration, sign-up, or limits. You can generate and validate unlimited schemas and JSON documents for personal, educational, or commercial projects without any restrictions.
Does it work offline?
Yes, once the page is loaded, all schema generation and validation happens entirely in your browser using JavaScript. No server communication is needed, so you can use it even without an internet connection after the initial page load.
Is my data secure?
Absolutely. All schema generation and validation happens directly in your browser using JavaScript. Your data is never sent to any server, stored, or logged. This ensures complete privacy and security for your API schemas, configuration files, and business data.