JSON Schema Validator
The JSON Schema Validator checks whether your JSON data matches a schema you write or paste, and lists every violation separately with its exact path inside the data (like $.user.age) and a clear message explaining why — not just a vague "invalid". It supports the JSON Schema Draft-07 keywords used in real-world schemas: type checking, required properties, allowed values (enum), limits for numbers/strings/arrays, string patterns, and the combinators allOf/anyOf/oneOf/not. Everything is validated by a parser written specifically for this site, entirely in your browser — your data and schema are never uploaded anywhere.
Both the data and the schema are processed entirely on your device and are never sent to a server.
The result will appear here after clicking "Validate"
What this tool does
Checks that JSON data matches a JSON Schema you supply, and reports every violation with its path inside the data.
When to use it
- Confirming an API response matches the agreed contract.
- Validating a config file before deploying it.
- Checking data produced by a language model against the shape you asked for.
- Testing a schema you wrote against real examples.
How to use it
- Paste the "JSON data" into its field.
- Paste the "JSON Schema" into its field.
- Click "Validate" and read the result: either an exact match, or the list of violations with each one's path.
A practical example
Input
A schema requiring a string field named email, with data that omits it.
Output
A message identifying the missing required field email, with its path inside the data.
Limitations
- What is supported is the common, practical subset of Draft-07: type, enum and const, object keywords (properties, required, additionalProperties, min/maxProperties), array keywords (items, min/maxItems, uniqueItems), string keywords (min/maxLength, pattern, a few formats), number keywords, and the combinators allOf, anyOf, oneOf and not.
- $ref resolution is not supported and no schema is fetched from the internet — deliberately: this tool makes no network requests at all.
- The format keyword is supported for a handful of the most common cases only.
- The schema itself must be valid JSON, and that is reported separately from data errors.
Privacy and processing
Both the data and the schema are processed entirely on your device and neither is ever sent to a server.
Technical notes
- The validator is written inside this project rather than taken from a library, because the real use case — does my data match the shape I described — is covered by a limited set of keywords without carrying a full specification.
Frequently Asked Questions
It supports the keywords used in most real-world Draft-07 schemas (type, required, limits, patterns, enum/const, and allOf/anyOf/oneOf/not composition), but it doesn't currently support $ref or fetching external schemas over the network.