JSON Schema Validator Online — Free, Instant, No Install
Need to check whether your JSON data matches a schema definition? Our JSON Schema Validator does it instantly, right in your browser. Paste your JSON on the left and your schema on the right, click Validate, and get a detailed report in milliseconds — no server, no sign-up, zero data leaves your machine.
This tool supports JSON Schema Draft-07, 2019-09, and 2020-12 and catches every rule violation: missing required fields, wrong types, format mismatches, enum violations, and more. Each error shows the exact path in your data where the problem occurred, so you fix issues fast.
How to Use the JSON Schema Validator
- Paste your JSON data into the left editor — this is the document you want to test.
- Paste your JSON Schema into the right editor — this defines the rules your data must follow.
- Select the schema version from the dropdown (Standard v7, 2019-09, or 2020-12).
- Click Validate — or press Shift+Enter from outside the editor — to run validation.
- Read the result: a green status means valid; a red status lists every error with its data path and message.
Use the Beautify button to auto-format both panes with 2-space indentation. Use Clear to reset everything and start fresh.
What Is JSON Schema?
JSON Schema is a vocabulary for annotating and validating JSON documents. It describes the expected structure of your data: which fields are required, what type each field must be, minimum and maximum values, allowed string patterns, enum options, and much more.
Think of a JSON Schema as a contract for your data. APIs publish schemas so every client knows exactly what shape the request and response bodies must take. CI pipelines validate config files against schemas to catch misconfiguration before deployment. Data engineers validate incoming records so a bad upstream row never breaks a downstream pipeline.
The specification is maintained at json-schema.org and is used by tools like OpenAPI (formerly Swagger), AWS CloudFormation, and Kubernetes CRDs.
Common Use Cases
- API contract testing: Validate request and response payloads against your OpenAPI schema before writing a single integration test.
- Config file validation: Ensure
package.json, CI/CD config, or infrastructure-as-code files match their expected shape before committing. - Data pipeline quality gates: Reject records that violate a schema before they enter a database or message queue.
- Form data validation: Define a schema for user-submitted data and validate it server-side without hand-writing type checks.
- SDK development: Ship a canonical schema alongside your SDK so consumers can validate their requests locally before hitting your API.
Supported JSON Schema Versions
This validator supports three draft versions:
| Version | Notes |
|---|---|
| Draft-07 | Most widely used. Adds if/then/else, readOnly, writeOnly, contentMediaType. |
| 2019-09 | Renamed keywords ($recursiveRef), vocabulary system, separated $id/$anchor. |
| 2020-12 | Adds prefixItems, unevaluatedItems, unevaluatedProperties, $dynamicRef. |
Select the version that matches the $schema keyword at the top of your schema file. When in doubt, Draft-07 covers the vast majority of real-world schemas.
Frequently Asked Questions
How do I validate JSON against a JSON schema online?
Paste your JSON document into the "JSON Data" editor and your schema into the "JSON Schema" editor, then click Validate. The tool parses both inputs, compiles the schema using the AJV library, and runs validation entirely in your browser. You get a pass/fail result plus a list of every error with the exact data path and rule that failed — no server call required.
What does a JSON Schema validation error look like?
Each error includes two pieces of information: the instance path (where the problem is in your JSON, e.g. /users/0/email) and the error message (what rule failed, e.g. must match format "email"). This lets you navigate directly to the offending field without scanning the entire document.
Which JSON Schema version should I use — Draft-07, 2019-09, or 2020-12?
Check the $schema property at the top of your schema file — it tells you which draft the schema was written against. If you are writing a new schema from scratch, Draft-07 is the safe default: it is supported by the broadest range of tools and libraries. Use 2019-09 or 2020-12 only when you need features they introduced, such as $dynamicRef in 2020-12.
Does this JSON Schema validator work without an account?
Yes. Everything runs client-side in your browser using the AJV library. No data is transmitted to any server. There is no account, no login, and no usage limit.
What are the most common JSON validation errors?
The most frequent errors are: missing required fields (a property listed in required is absent from the data), type mismatches (a field expected to be "integer" contains a "string"), format violations (a field with "format": "email" does not match the email pattern), and JSON syntax errors (trailing commas, single quotes instead of double quotes, unquoted keys). Fix syntax errors first — the validator cannot run schema validation until the JSON itself is parseable.
Can I validate JSON5 or JSON with comments?
No. This tool follows the strict JSON specification (RFC 8259). JSON5 extensions — comments, trailing commas, single-quoted strings, unquoted keys — are not valid JSON and will cause a parse error before schema validation begins. Convert JSON5 to standard JSON first using a dedicated converter.
Resources
- json-schema.org — Official JSON Schema specification and documentation, including the full vocabulary reference for each draft version.
- AJV — Another JSON Schema Validator — The library powering this tool. Excellent reference for understanding how schemas are compiled and errors are reported.
- Understanding JSON Schema (Read the Docs) — A beginner-friendly guide that explains every keyword with examples, from basic types to complex combinators like
allOf,anyOf, andoneOf.
