JSON Schema Validator Online – Validate JSON Against Schema

How to Validate JSON Against a Schema

JSON Schema acts as a “contract” for your data, ensuring that the JSON you send or receive matches a specific structure. Here is how to use this validator:

1. Step 1: Input Data: Paste the JSON object you want to test in the left-hand box (the “Instance”).
2. Step 2: Input Schema: Paste your JSON Schema definitions in the right-hand box. This defines the rules (types, required fields, formats).
3. Step 3: Validate: Click the “Validate Data” button. Our engine will cross-reference every property against your rules.
4. Step 4: Debug: If the data is invalid, the tool provides a detailed error report, pinpointing exactly which field failed and why (e.g., “Property ‘price’ should be number, found string”).

Supported JSON Schema Keywords

Our validator supports the core specification of JSON Schema Draft 7, covering the most essential validation logic used in modern REST APIs.

1. Type Validation

The `type` keyword is the foundation of any schema. It restricts the data type of a value.

• "type": "string" – Accepts text (e.g., “Hello”).
• "type": "integer" – Accepts whole numbers only (e.g., 42).
• "type": "number" – Accepts integers and decimals (e.g., 42.5).
• "type": "boolean" – Accepts `true` or `false`.
• "type": "array" – Accepts a list of items `[…]`.
• "type": "object" – Accepts a key-value map `{…}`.

2. Object Constraints

When validating objects, you can enforce specific structures:

• properties: Defines the keys allowed in the object.
• required: An array of strings listing keys that MUST be present.
• additionalProperties: Set to `false` to ban any keys not explicitly defined in `properties`.

3. Value Constraints

You can further restrict the values within a type:

• enum: The value must match one of the items in this list (e.g., `[“red”, “green”, “blue”]`).
• const: The value must match this exact constant.
• minLength / maxLength: Restricts string length.
• minimum / maximum: Restricts numeric ranges.

JSON Validation vs. Schema Validation

It is important to understand the difference between a syntax check and a schema check.

Why Use Our Client-Side Validator?

1. Enterprise-Grade Privacy

Validation often involves checking production data, customer records, or internal API contracts. Unlike other online tools that send your schemas to a backend server, this validator runs 100% in your browser. Your proprietary schemas and data never leave your device.

2. Instant Feedback Loop

Because there is no server round-trip, validation happens in milliseconds. This allows you to rapidly prototype and iterate on your schemas without waiting for a network request to finish.

3. Human-Readable Errors

Cryptic error messages are frustrating. Our engine translates validation failures into plain English sentences like “Missing required property: user.email” instead of generic error codes.

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Frequently Asked Questions