---
title: "JSON Schema Validator - Test Data Online | CanDoYa"
description: "Validate JSON data against a JSON Schema online. See every failed rule with its exact data path. Free, private and no sign-up required."
url: https://candoya.com/tools/json-schema-validator/
locale: en
type: browser-tool
---

# Free JSON Schema Validator

Category: Developer

## What is a JSON Schema validator?

A JSON Schema validator checks whether JSON data follows rules for types, required fields, ranges, patterns and object structure. Paste a schema and a data document to see every mismatch with its exact path. Validation runs locally in your browser, so API payloads and configuration data are not uploaded.

This validator supports JSON Schema Draft 2020-12 through Ajv. It first checks that both editors contain valid JSON, then compiles the schema and tests the data against every applicable rule. The report groups failures by data path so you can move from a broad invalid result to a specific field.

## How to use it

1. **Paste the schema** - Add a valid JSON Schema to the left editor. Draft 2020-12 keywords are supported.
2. **Paste the data** - Add the JSON document you want to test to the right editor.
3. **Validate the document** - Choose Validate data, or press Ctrl+Enter or Cmd+Enter, to compile the schema and run every check.
4. **Fix each path** - Use the reported data paths and keyword labels to correct the data or refine the schema.

## Who it's for

- **API developers** checking request and response examples against a published contract.
- **Frontend teams** testing form output before it reaches an endpoint.
- **Platform engineers** reviewing configuration files and event payloads before deployment.
- **Schema authors** trying required fields, enums, bounds and nested object rules against realistic data.

## Expert note

A valid JSON document can still fail a JSON Schema: syntax validation only proves that JSON.parse can read it, while schema validation also checks constraints such as required, type, enum, minimum and additionalProperties.

## Frequently asked questions

### Is the JSON Schema validator free?

Yes. You can validate schemas and JSON data for free with no account or sign-up. The tool reports all detected validation failures in one run instead of stopping after the first mismatch.

### Is my JSON data uploaded?

No. The schema compiler and validator run inside your browser. The schema and data entered in the editors are not sent to a validation server, which is useful for private API payloads, configuration and test fixtures.

### How much JSON can I validate?

There is no fixed tool limit. Practical capacity depends on your browser, device memory and schema complexity. Normal API payloads and configuration files should validate quickly, while deeply recursive schemas or very large documents may take longer.

### Which JSON Schema draft does this support?

The validator uses Ajv's JSON Schema Draft 2020-12 implementation. It also handles the core validation vocabulary used for types, objects, arrays, strings, numbers, conditional rules and references that can be resolved within the supplied schema.

### What is the difference between JSON validation and JSON Schema validation?

JSON validation checks syntax such as quotes, commas and brackets. JSON Schema validation starts with valid JSON, then checks whether the values and structure follow a separate contract. A payload can have perfect JSON syntax and still fail a required field or type rule.

### Can the validator resolve a remote $ref?

No. This browser tool does not fetch remote schemas. Local references within the pasted schema can resolve, but an external $ref needs its referenced schema to be bundled locally or handled by a validator configured with that dependency.

## Related tools

- [JSON Validator](https://candoya.com/tools/json-validator/)
- [JSON Formatter](https://candoya.com/tools/json-formatter/)
- [YAML Validator](https://candoya.com/tools/yaml-validator/)
- [JSON Minifier](https://candoya.com/tools/json-minifier/)
- [JSON to YAML Converter](https://candoya.com/tools/json-to-yaml/)

---

*Markdown edition of <https://candoya.com/tools/json-schema-validator/>, published for AI agents and other automated readers. Index of key pages: <https://candoya.com/llms.txt>.*