JSON Schema Validator Validate JSON Data Against Your Schema — Instant, Private, Free

A vocabulary for annotating and validating JSON documents. It describes the structure, types, and constraints your JSON must follow. Used in API documentation (OpenAPI), form validation, and data pipelines. Current stable versions: Draft 7 and Draft 2020-12.

Paste your JSON Schema in the left editor and JSON data in the right editor. The validator checks every constraint and shows errors with JSON paths. Click any error to navigate to that location. All validation runs in your browser — no data sent to any server.

type, required, properties, additionalProperties, patternProperties, pattern, minLength, maxLength, minimum, maximum, exclusiveMinimum, exclusiveMaximum, multipleOf, enum, const, minItems, maxItems, uniqueItems, items, contains, anyOf, oneOf, allOf, not, if/then/else, dependencies, contains, propertyNames, format. See the keyword reference table above.

An array of property names that must be present in the object. Example: {"required": ["name", "email"]} means both name and email must exist as keys. If either is missing, validation fails with a "Required property is missing" error.

Controls whether extra properties (not in the properties map) are allowed. additionalProperties: false rejects any unknown keys. additionalProperties: {type: string} validates extra properties against that schema. Omitting it allows any additional properties.

anyOf: valid if any one schema matches. oneOf: valid if exactly one schema matches — zero or two+ matches fails. Use anyOf for flexible union types. Use oneOf for exclusive choice between mutually exclusive structures.

Annotates a string with a semantic format. This validator enforces: email, uri, date, date-time, time, uuid, ipv4, ipv6, hostname, regex, json-pointer. Format validation is optional in the spec — some validators ignore it.

Paste schema left, JSON right. Validates instantly in your browser. Error list with JSON paths. Format button for both editors. 5 presets. Free, no account. No data sent to any server.

number accepts any JSON number including decimals (1.5, 3.14). integer accepts only whole numbers (1, 42, -7). Use integer for IDs, counts, ages. Use number for prices, coordinates, measurements.

Use {"type": "array", "items": {object schema here}}. The items schema applies to every element. Add minItems/maxItems for length constraints and uniqueItems: true to require all items to be distinct.

A URI declaring which JSON Schema version to use. Use "http://json-schema.org/draft-07/schema#" for Draft 7. Including $schema is best practice — it enables IDE autocompletion and ensures validators apply the right rules.

If data matches the if schema, the then schema is also applied. If not, the else schema (if present) is applied. Used for conditional required fields: if type is "premium" then billing is required.

Restricts a value to one of the listed values: {"enum": ["active", "inactive", "pending"]}. For a single allowed value, use const instead: {"const": "active"}.

Use properties with a sub-schema for each property. Each sub-schema can itself have type, required, and properties for deeper nesting. There is no nesting limit in JSON Schema.

Foundation of OpenAPI (Swagger) specifications. Used to document every request and response body. Tools like Postman, API gateways, and mock servers use the schema to generate tests and client SDKs. Also used in form validation, MongoDB document validation, Kafka message validation, and configuration linting.

Paste schema and data in the editors above. Validates instantly in your browser. Nothing sent to any server. Error list with paths. Format button. 5 ready-made presets. Free, no signup, no account.