JSON Schema Validator
Validate JSON data against a documented JSON Schema validation subset. Runs locally in your browser.
What this validator does
Paste a JSON document and a JSON Schema, then validate the data against supported schema constraints. Errors include the data path, schema path, keyword, and a human-readable explanation.
Supported validation areas
The implementation covers common Draft 2020-12 validation needs including type, enum, const, required properties, properties, patternProperties, additionalProperties, array items and prefixItems, array length and uniqueness, string length and pattern, numeric bounds and multiples, composition with allOf/anyOf/oneOf/not, conditional if/then/else, and local definitions through $defs or definitions.
A useful validation workflow
- Parse and confirm the JSON data is valid.
- Paste the schema that describes the expected structure.
- Click Validate and inspect each data/schema path when errors are reported.
- Fix the source data or schema and validate again.
Important limitation
JSON Schema is a large specification. This Odelvo tool deliberately documents a supported validation subset rather than pretending to implement every vocabulary, format, remote reference, or extension. Only the 2020-12 dialect URI is accepted. References must point directly to root $defs or definitions entries; remote references, $id, format and unevaluatedProperties are rejected. Unknown keywords, malformed constraints and unresolved references are checked even in unused branches. Validation stops with an error at the nesting limit of 128. Numbers use JavaScript precision; non-finite numbers and integers outside its safe range are rejected. A VALID result applies only to this supported subset.
Frequently asked questions
- Which JSON Schema draft does this validator support?
- The validator is designed around the Draft 2020-12 vocabulary and implements a documented subset of its validation keywords. It does not claim full Draft 2020-12 conformance, and unsupported keywords are reported instead of silently ignored.
- What is the difference between JSON syntax validation and schema validation?
- JSON syntax validation checks whether the text is valid JSON. Schema validation starts with parsed JSON data and checks whether that value satisfies constraints such as type, required properties, ranges, lengths, arrays, enums, and composition rules.
- Why can valid JSON still fail schema validation?
- A JSON document can be perfectly valid JSON while violating its schema. For example, a required property may be missing, a number may be below minimum, a string may not match a pattern, or an object may contain a property rejected by additionalProperties.
- Is my JSON uploaded anywhere?
- No. Validation happens in the browser. The tool does not send the JSON data or schema to a remote validation service.
- Does this validator support every JSON Schema keyword?
- No. To avoid misleading results, unsupported keywords are rejected with an explanation rather than treated as if they were enforced.