JSON Schema Validator
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Jsonic's JSON Schema Validator checks a JSON document against a JSON Schema (draft-07 subset). Paste your schema on the left and your JSON instance on the right, then click Validate. It checks type constraints, required fields, string formats (email, date, URI), minimum/maximum, minLength/maxLength, pattern, enum, const, additionalProperties, allOf, anyOf, oneOf, and not. All validation runs in your browser — your data is never uploaded.
How to validate JSON against a schema
- Paste your JSON Schema into the left panel (or click "Valid Example" to load one).
- Paste the JSON you want to validate into the right panel.
- Click Validate.
- If validation fails, the error list shows each problem with its path and message.
- Fix the JSON and click Validate again until it passes.
FAQ
What is JSON Schema?
JSON Schema is a vocabulary that allows you to annotate and validate JSON documents. It defines the expected structure, types, and constraints of your data — commonly used for API request/response validation, config files, and data pipelines.
Which JSON Schema version does this support?
This validator supports the most common JSON Schema draft-07 keywords: type, required, properties, additionalProperties, items, minItems/maxItems, minLength/maxLength, minimum/maximum, exclusiveMinimum/exclusiveMaximum, pattern, format (email, date, date-time, uri), enum, const, allOf, anyOf, oneOf, and not.
What formats are supported?
email, date (YYYY-MM-DD), date-time (ISO 8601), and uri (must start with http:// or https://).
Is my data uploaded anywhere?
No. Validation runs entirely in your browser using JavaScript. Your schema and JSON never leave your machine.
How do I define required fields?
Add a "required" array to your schema with the field names: { "required": ["id", "name"], "properties": { ... } }.
What does additionalProperties: false do?
It rejects any property in the JSON instance that is not explicitly defined in the "properties" keyword of the schema.
Recommended reading
- Designing Data-Intensive Applications (2nd Edition) — Martin Kleppmann & Chris RiccominiThe modern classic on data systems — encoding formats, schemas, replication, and stream processing.
- JavaScript: The Definitive Guide (7th Edition) — David FlanaganThe complete reference for the language JSON came from — serialization, async, and the full standard library.
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