JSON Schema Validation · Local Browser Tool

JSON Schema Validator Online

Validate a JSON instance against a JSON Schema in your browser. Get separate schema and instance errors with JSON paths, approximate line numbers, and suggested fixes.

Validate JSONSupported keywords

No upload: parsing and validation happen locally in this browser tab. This is a focused common-keyword checker, not a complete replacement for an authoritative JSON Schema library.

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Field-level results

See whether the problem is in the schema or the JSON instance.

Browser-side validator

Check schema and instance together.

Use the example to see valid data, then introduce a type or required-field error. The tool accepts JSON only and keeps both inputs in this tab.

Load an example or paste a JSON Schema and JSON instance.

Validation resultsREADY

No validation run yet.

Scope and workflow

Validate, then test the payload.

Use the validator for fast local feedback, then move the JSON into the rest of your QA workflow.

OpenAPI Validator

Check OpenAPI 3.0 and 3.1 documents, paths, responses, and references.

API Integration Testing

Send a CORS-enabled REST request, assert the response, and copy a report.

Test Data Generator

Generate fictional JSON, CSV, or SQL fixtures for API payloads and QA cases.

CSV to JSON Converter

Convert local CSV files into JSON before checking them against a schema.

API Contract Testing

Compare schema versions for removed fields, type changes, and new required fields.

Test Plan Template

Document schema scope, test data, environments, risks, and exit criteria.

Supported JSON Schema keywords

This lightweight validator recognizes Draft-07 and 2020-12 identifiers and checks common type, properties, required, additionalProperties, items, enum, const, minimum, maximum, minLength, maxLength, pattern, minItems, maxItems, uniqueItems, allOf, anyOf, oneOf, not, and local $ref. It intentionally does not claim full dialect, format, dynamic reference, annotation, or vocabulary coverage.

JSON Schema validator FAQ

What is JSON Schema validation?

It checks whether a JSON instance matches rules defined by a JSON Schema, such as required fields, types, allowed values, and array or string constraints.

Why are schema errors separate from instance errors?

A malformed or unsupported schema cannot reliably validate data. The report labels schema problems separately so you know whether to fix the rules or the JSON payload.

Are line numbers exact?

For JSON, the tool reports the nearest key or path line in the pasted text. Use the path as the precise locator, especially when the same property name appears more than once.

Is my data uploaded?

No. The page does not call a validation API. Keep the tab private and follow your organization’s policy for sensitive payloads.