JSON Schema Validator (Draft 7 / 2019-09 / 2020-12)
JSON Schema is the standard contract for JSON data: required fields, type constraints, value ranges, and format hints like email or uri. Validating against a schema catches issues at the edge of a system before they corrupt anything downstream. This tool runs the well-tested ajv 8 validator with the ajv-formats extension, supports all three modern draft versions, and reports every error with an exact instance path so you can pinpoint and fix issues fast.
What JSON Schema Validates
A JSON Schema describes the shape a JSON document must have: required properties, allowed types per property, value ranges for numbers, length limits for strings, pattern matches for identifiers, format checks for emails and URIs, conditional rules with if/then/else, and structural rules with oneOf/anyOf/allOf. Validating a document against a schema either confirms the document conforms or produces a list of errors, each with the exact path inside the instance (/items/0/price), the failed keyword (type, required, format), and a human-readable message.
Why ajv 8 in the Browser
ajv is the de-facto reference implementation of JSON Schema in the JavaScript world. It is the validator behind ESLint, OpenAPI tooling, Fastify, Express middleware, and most major Node.js libraries that care about validation. Version 8 supports JSON Schema Draft 7, Draft 2019-09, and Draft 2020-12 — the three modern versions — plus the ajv-formats extension which adds date, date-time, email, hostname, ipv4, ipv6, uri, uuid, and a dozen others. Running the same validator in the browser means the verdict you see here matches what your production validator will say.
How to Use the Tool
Paste the schema into the left panel and the document into the right. Pick the draft (Draft 7 is the most common for established projects; 2020-12 is the newest). Optional: enable strict mode, which rejects schemas with unknown keywords — useful to catch typos in custom keywords. Hit Validate and see one of two outcomes: a green pass with the schema title (if any), or a red fail with every error listed. Each error shows the instance path, the schema path, the failed keyword, and the message ajv generated. Fix the document or the schema and re-validate.
Use Cases for Browser Validation
Three patterns: First, debugging a failing API contract — paste the schema your service expects and a payload you cannot get accepted, and see exactly which field violates which rule. Second, schema authoring — write a draft schema and validate sample documents against it iteratively to make sure the rules say what you mean. Third, learning JSON Schema — the immediate feedback loop is more useful than reading the spec when figuring out how oneOf interacts with required. All three benefit from a tool that runs locally and lets you paste real (often sensitive) data without it leaving the tab.
Pair this validator with: JSON Schema Generator to draft a schema from a sample document, JSON Formatter for inspecting the document or schema, JSON to CSV (Deep) if the next step after validation is a flat CSV, and Schema.org Validator for the distinct case of validating JSON-LD against Schema.org types.
Frequently Asked Questions
Built by Derek Giordano · Part of Ultimate Design Tools