Validate JSON against a JSON Schema, right in your browser

Why JSON Schema validation matters

JSON Schema describes the shape of a JSON document — required fields, types, enums, formats, and combinations like oneOf. Validation turns informal API documentation into an automated, machine-checkable contract.

This page never sends your schema or data anywhere. Validation runs inside your browser using Ajv compiled to JavaScript at runtime.

When Ajv is useful

• Enforcing API request/response contracts at the edge and between microservices.
• Driving complex form validation without scattering ad-hoc if/else checks across the codebase.
• Validating configuration files (CI, infra, feature flags) before they ship to production.
• Gating data pipelines so malformed records fail fast with explicit, structured errors.

FAQ

Does this page send my schema or data to a server?

No. Validation runs in-browser with Ajv. The page works offline once loaded and the inputs never leave your tab.

Which JSON Schema draft does the playground use?

Ajv defaults to draft-07 here. Schemas with $schema set to a newer draft still validate the instance, but draft-specific keywords may need an Ajv build that opts into them.

Why do I sometimes see multiple errors for the same field?

Ajv is configured with allErrors: true, so it reports every violation instead of stopping at the first one. That makes it easier to see the full picture when fixing a payload.

How are formats like email or uuid checked?

Formats are provided by the ajv-formats package, which is loaded together with Ajv. The list includes email, uri, uuid, date, date-time, ipv4, ipv6, regex, and a few more.

Edge cases worth knowing

• $ref to remote schemas is not loaded by the playground — keep schemas self-contained or paste referenced definitions inline.
• oneOf and anyOf can produce many errors at once because Ajv reports each branch that fails — read errors top-down.
• Formats are advisory in JSON Schema; ajv-formats opts you in, but custom string formats still need a custom registration.
• Large schemas compile once per validate() call here for simplicity; in production you should cache the compiled validator.

How Ajv compares to other validators