JSON Schema Validator

What is JSON Schema?

JSON Schema is a vocabulary for describing the structure, types, and constraints of JSON data. A schema can require certain properties, restrict values to specific types, enforce minimum and maximum numbers, validate string formats like email addresses, and much more. It is the standard way to document and enforce the shape of JSON used by APIs and configuration files.

Our JSON Schema Validator is powered by Ajv, the most widely used JSON Schema engine in the JavaScript ecosystem. It compiles your schema and validates your data against it, collecting every violation rather than stopping at the first one.

How to Validate JSON

• Paste your JSON Schema into the left pane, or click Sample for an example
• Paste the JSON data to check into the right pane
• Validation runs instantly — a green banner confirms valid data
• If the data is invalid, each error is listed with its path and reason
• Errors in the schema or data JSON itself are reported separately and clearly

Understanding Validation Errors

Each validation error shows an instance path — pointing to the exact location in your data that failed, such as /age or /address/zip — alongside a human-readable message like must be >= 0 or must have required property 'name'. This makes it straightforward to locate and fix problems even in large, deeply nested documents.

Because all errors are collected at once, you can fix every issue in a single pass instead of repeatedly re-running validation after each individual fix.

Who Uses a JSON Schema Validator?

API developers use it to verify that request and response bodies conform to their documented contracts. DevOps engineers validate configuration files before deployment to catch mistakes early. QA engineers build it into test suites to guard against regressions. Everything runs locally in your browser, so your schemas and data stay completely private.

What JSON Schema Can Enforce

JSON Schema is far more expressive than a simple type check. It can require that specific properties are present, restrict each property to a particular type, and reject any unexpected additional properties. For numbers it can set minimums, maximums, and multiples; for strings it can enforce minimum and maximum length, a regular-expression pattern, or a named format such as email, date-time, or URI. For arrays it can require a minimum number of items, enforce uniqueness, and validate the shape of each element.

It also supports composition through keywords like allOf, anyOf, oneOf, and not, so you can describe complex conditional rules — for example, requiring one set of fields only when another field has a certain value. Because Ajv implements the full specification, this validator handles all of these constructs, which means the schema you test here behaves the same way it will in your application's validation layer.

Why Choose Our JSON Schema Validator?

This validator is completely free, needs no signup, and runs entirely in your browser. It is powered by Ajv, the most widely used JSON Schema engine in the JavaScript world, so its results match what your production code will do. It collects every validation error at once rather than stopping at the first, and reports each with the exact path in your data, so fixing problems is fast even in large documents.

The JSON Schema Validator is one of more than 200 free tools on ToopTools. If you work with schemas and API contracts regularly, you can pin it to your personalized My Workspace workspace so it sits beside your other developer utilities, always one click away. It works on any modern browser, on desktop and mobile.

Is the JSON Schema validator free?

Yes. It is completely free with no limits and no signup. You can validate as much JSON against as many schemas as you like, as often as you like, without ever creating an account.

Which version of JSON Schema does it support?

The validator is built on Ajv, which supports the modern JSON Schema drafts used across the ecosystem. Because it uses the same engine that powers countless production applications, a schema that validates here will behave consistently in your own Ajv-based validation.

Does it show all errors or just the first?

It collects and lists every validation error at once, not just the first failure. Each error includes the instance path pointing to the exact location in your data and a human-readable message, so you can fix all the problems in a single pass instead of re-running validation repeatedly.

What do the error paths mean?

Each error shows an instance path such as /age or /address/zip, which is a pointer to the precise field in your data that failed. Paired with a message like 'must be >= 0' or 'must have required property name', it tells you exactly what to change, even in deeply nested documents.

Is my data private?

Completely. Both your schema and your data are validated locally in your browser, so nothing is uploaded, logged, or stored on a server. It is safe to use with proprietary schemas and confidential data.

Who Uses a JSON Schema Validator?

• API developers verifying request and response bodies against their documented contracts
• DevOps engineers validating configuration files before deployment
• QA engineers building schema checks into automated test suites
• Teams documenting and enforcing the agreed shape of shared JSON data
• Anyone debugging why a payload is being rejected by a strict endpoint

Key Features

• Powered by Ajv, the industry-standard JSON Schema engine
• Validates data against your schema and lists every error at once
• Each error shows its exact instance path and a readable message
• Reports problems in the schema or data JSON itself separately and clearly
• Instant validation as you edit either pane
• 100% browser-based — your schema and data never leave your device

How do I validate JSON against a schema?

Paste your JSON Schema in one box and the JSON you want to check in the other. The tool validates instantly and lists every error with the exact path to the problem, so you can see which fields fail and why, then fix them and re-check.

Does the JSON Schema validator work offline?

Yes. Validation runs entirely in your browser, so once the page has loaded the tool works without an internet connection and neither your schema nor your data is ever uploaded — safe for proprietary data structures.