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JSON Formatter & Validator
Format and validate JSON syntax — paste raw JSON to get it properly indented and catch syntax errors before schema validation.
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Free JSON Schema Validator Online
Validate any JSON document against a JSON Schema. Supports Draft 3, 4, 6, 7, 2019-09, and 2020-12 — including modern features browser-only tools miss. Server-side. Nothing stored.
Processed on our server — your JSON is never stored or logged.
JSON Document
JSON Schema
Paste JSON into both panes and click Validate.
Tip: Ctrl+Enter / Cmd+Enter triggers Validate from anywhere in the panes.
Tip: Ctrl+Enter / Cmd+Enter triggers Validate from anywhere in the panes.
About JSON Schema Validator
JSON Schema Validator checks that a JSON document conforms to a JSON Schema definition. Paste or upload your JSON document in the left pane and your JSON Schema in the right pane, choose a draft version (or let the tool auto-detect from the $schema keyword), then click Validate. Results appear instantly — a green banner if the document is valid, or a table of exact errors with the path, human-readable message, and the failing schema keyword.
This tool runs server-side using a native PHP validator that supports all major JSON Schema drafts including Draft 3, 4, 6, 7, 2019-09, and 2020-12. Coverage includes all Draft 3–7 keywords and the core Draft 2019-09/2020-12 assertions — including if/then/else, const, contains, propertyNames, prefixItems, and numeric range keywords. Vocabulary-based extensions (unevaluatedProperties, $dynamicRef) are not implemented.
Common use cases
- Validate an API response payload against the schema your team published in OpenAPI or AsyncAPI.
- Debug a schema you're writing: paste a known-good document and see which keywords trigger unexpected errors.
- Verify that a configuration file (GitHub Actions, AWS CloudFormation, etc.) matches its schema before committing.
- Test a
required+typeguard before shipping a data contract to a downstream team. - Compare behaviour between Draft 7 and Draft 2020-12 schemas side by side.
Frequently asked questions
What is JSON Schema?
JSON Schema is a vocabulary for annotating and validating JSON documents. A schema describes the structure of a JSON value — which fields are required, what types they must have, what ranges are acceptable, and how nested objects or arrays should be shaped. It is widely used to document APIs, validate configuration files, and generate UI forms from data contracts.
How do I validate JSON against a schema online?
Paste your JSON document in the left pane and your JSON Schema in the right pane on this page. Select a draft version or leave it on Auto-detect (the tool reads the $schema keyword from your schema). Click Validate. If the document is valid, a green banner confirms it. If not, the error table shows the exact path inside the document, the human-readable message, and the failing JSON Schema keyword.
What is the difference between JSON Schema Draft 7 and Draft 2020-12?
Draft 2020-12 is the most recent stable release. It introduces prefixItems (replaces items for positional array validation), unevaluatedProperties and unevaluatedItems (stricter "no extra keys" constraints), and a formal vocabulary system that makes extensions more predictable. Draft 7 is the most widely deployed version and is supported by the largest number of libraries. If you are writing a new schema and your tooling supports it, Draft 2020-12 is the recommended choice.
What does "required property missing" mean in JSON Schema?
The required keyword lists property names that must be present in an object. If your schema has "required": ["name", "email"] and the document's object does not include the "name" key, validation fails with a "required property missing" error at the path of the object (e.g. "/" for the root, or "/user" for a nested object). Adding the missing key to the document or removing it from required resolves the error.
Can I validate a large JSON file against a schema?
Yes. File upload is supported for both panes — click "or upload .json" below each textarea. Files up to 20 MB are accepted. For very large documents the validation still runs server-side, so no client memory limit applies.
Is my JSON data uploaded to a server?
Yes — both the document and the schema are sent to our server for validation. The server processes them in memory and returns the result. Nothing is written to disk or retained after the response is sent. No account or session tracking is used.
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