Validate JSON data against a JSON Schema (Draft 7) with detailed error reporting. Free browser-based tool with sample schemas and path-level diagnostics.
Paste your JSON data into the left editor panel.
Paste a JSON Schema into the right panel, or select a sample schema from the dropdown.
Click Validate to check the data against the schema.
Review any validation errors — each shows the path, the violated keyword, and a clear message.
Validates type, required, properties, items, enum, pattern, min/max, allOf/anyOf/oneOf, $ref, and more.
Each error identifies the exact JSON path where the violation occurred, making it easy to fix issues.
Pre-built schemas for API responses, package.json, and config files to get started instantly.
All validation runs locally in your browser — your data and schemas are never sent to any server.
JSON schemas often validate production API payloads, configuration files with credentials, and healthcare or financial data. Because this validator runs entirely in your browser, neither your data nor your schema is ever transmitted to an external server. There is zero risk of data exposure, making it safe for HIPAA-sensitive, PCI-regulated, or confidential enterprise data.
When validation fails, every error includes the exact JSON Pointer path (e.g., $.users[0].email), the violated keyword (e.g., format), and a human-readable message. This precision eliminates guesswork — you know exactly where the problem is and what rule was broken, even in deeply nested structures with hundreds of fields.
The validator supports all core JSON Schema Draft 7 keywords including type, required, properties, additionalProperties, items, enum, const, pattern, format, minimum, maximum, minLength, maxLength, allOf, anyOf, oneOf, not, and local $ref resolution. This coverage handles real-world schemas used in production API contracts.
Start validating immediately — no account creation, no email verification, no daily caps. Validate a single object or run hundreds of checks per session with no restrictions. Sample schemas are included so you can explore the tool's capabilities without writing a schema from scratch.
JSON Schema is a powerful vocabulary for annotating and validating JSON documents. It defines the expected structure, data types, constraints, and relationships within a JSON payload. Originally designed to describe API contracts, JSON Schema is now used across configuration management, form generation, documentation, and data quality enforcement.
A JSON Schema is itself a JSON document that describes the expected shape of another JSON document. It specifies which properties should exist, what types they should have, what values are acceptable, and how nested structures should be organized. The schema acts as a contract — any JSON document that conforms to the schema is considered valid.
JSON Schema Draft 7 defines several categories of validation keywords:
type keyword restricts values to specific types (string, number, integer, boolean, null, array, object). Union types are supported: "type": ["string", "null"] allows either.minLength, maxLength, pattern (regex), and format (email, date, uri, uuid, ipv4, ipv6) validate string content.minimum, maximum, exclusiveMinimum, exclusiveMaximum, and multipleOf enforce numeric ranges.required lists mandatory properties. properties defines per-property schemas. additionalProperties controls whether unlisted keys are allowed.items validates each element. minItems, maxItems, and uniqueItems enforce collection rules.allOf (must match all), anyOf (must match at least one), oneOf (must match exactly one), and not (must not match) combine sub-schemas for complex validation.$ref with JSON Pointer syntax enables schema reuse by referencing definitions elsewhere in the document.Always set additionalProperties: false when you want strict validation — otherwise, unlisted keys pass silently. Use $ref to define reusable sub-schemas in a definitions block, keeping schemas DRY and maintainable. Include description fields in your schema for self-documenting contracts. Test schemas against both valid and invalid data to ensure constraints work as intended.
JSON Schema has evolved through several drafts, each adding capabilities. Draft 4 introduced the core vocabulary that most developers learned first. Draft 6 added const (exact value match), contains (at least one array item matches), and propertyNames (validate key names). Draft 7 added if/then/else conditional validation, readOnly/writeOnly annotations, and contentMediaType for describing encoded string content. The latest drafts (2019-09 and 2020-12) introduced vocabularies, dynamic references, and unevaluatedProperties for stricter composition. Draft 7 remains the most widely deployed version and is recommended for most production use cases due to its excellent tooling support across all major programming languages.
Several validation patterns appear repeatedly in real-world schemas. Nullable fields use "type": ["string", "null"] to allow either a value or null. Discriminated unions use oneOf combined with a constant type field to validate polymorphic objects — for example, a payment object that can be either a credit card or bank transfer, each with different required fields. Dependent required fields use the dependencies keyword to require certain fields only when other fields are present, such as requiring a billing address only when a payment method is provided. Enumerated constants use enum arrays to restrict values to a predefined set, commonly used for status fields, country codes, and configuration options. Mastering these patterns enables you to express complex business rules declaratively rather than writing custom validation logic in application code.
JSON Schema is a standard vocabulary (currently at Draft 7 / Draft 2020-12) that defines the expected structure, types, and constraints of a JSON document. It is itself written in JSON and acts as a contract — any JSON document that conforms to the schema is considered valid. JSON Schema is used for API validation, configuration checking, form generation, and documentation.
Yes. All validation processing happens locally in your browser using JavaScript. Neither your JSON data nor your schema is transmitted to any server, logged, or stored. This makes the tool safe for validating sensitive payloads including API tokens, medical data, financial records, and internal configuration files.
The tool supports JSON Schema Draft 7 core validation keywords including type, required, properties, additionalProperties, items, enum, const, pattern, format, minimum, maximum, exclusiveMinimum, exclusiveMaximum, minLength, maxLength, minItems, maxItems, uniqueItems, minProperties, maxProperties, allOf, anyOf, oneOf, not, and local $ref resolution.
Each error shows three pieces of information: the path (e.g., $.users[0].email) identifying exactly where in your JSON the problem is, the keyword (e.g., format, required, type) identifying which schema rule was violated, and a human-readable message explaining the issue. Fix the errors from top to bottom.
The sample schemas dropdown provides pre-built schemas for common use cases: an API response schema (with status, data array, and meta object), a package.json schema (validating npm package structure), and a config file schema (with app settings, database, and logging). They help you explore the tool's capabilities without writing a schema from scratch.
Yes. The validator recursively checks nested objects and arrays at every depth level. If a nested property violates its schema, the error path shows the full path (e.g., $.config.database.port) so you can locate the issue precisely.
When additionalProperties is set to false in a schema, any property in the JSON data that is not listed in the properties object will cause a validation error. This is useful for strict API contracts where unexpected fields should be rejected rather than silently accepted.
Yes. The tool supports local $ref references using JSON Pointer syntax. Define reusable sub-schemas in a definitions block and reference them with $ref: '#/definitions/address'. This keeps schemas DRY and is the standard approach for complex, production-grade schemas.
The format keyword supports: email, date (YYYY-MM-DD), date-time (ISO 8601), uri, ipv4, ipv6, and uuid. Unknown formats are silently accepted per the JSON Schema specification, which treats format validation as optional by default.
Yes. There are no file size or complexity limits. Validation runs entirely in your browser, so the practical limit depends on your device's memory. Most modern devices handle documents with thousands of properties across deep nesting levels without issues.
Explore practical JSON Schema examples for user registration APIs, product catalogs, app configs, and CI/CD pipelines with reusable patterns.
Read more →Learn JSON Schema Draft 7 validation including types, required fields, patterns, and composition keywords. With practical examples for API contracts.
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