JSON Schema Generator
Generate a complete JSON Schema Draft-07 or Draft 2020-12 from any JSON payload instantly in your browser. Infers types, required fields, string formats, and nested object structures. Fully client-side — your data never leaves your device.
Paste or upload a JSON payload to instantly generate a complete JSON Schema. Supports Draft-07 and Draft 2020-12 with configurable required fields, format detection, and description placeholders. All processing happens locally in your browser.
Optional title added to the root schema object
Instant Schema Inference
Generate a complete JSON Schema from any JSON payload in milliseconds. The engine traverses every nested object and array, infers types, detects string formats, and builds a fully structured schema without any server processing.
Complete Data Privacy
Your JSON payloads never leave your device. All schema generation runs locally in your browser, making this tool safe for API responses, database records, and any sensitive business data you need to document.
Draft-07 & Draft 2020-12
Choose between JSON Schema Draft-07 (widely supported by validators like AJV and jsonschema) and the modern Draft 2020-12 specification. Both outputs include the correct $schema URI, required arrays, and format annotations.
100% Free, No Limits
No subscriptions, no file size caps, no usage quotas, and no account required. Generate JSON Schemas from payloads of any size as many times as you need, completely free forever.
API Documentation
Generate JSON Schemas from real API response payloads to document request and response bodies in OpenAPI specifications. Paste a live API response and get a ready-to-use schema that accurately reflects the actual data structure your endpoints return.
Runtime Validation
Create validation schemas for AJV, jsonschema, or Zod from existing JSON data. Use the generated Draft-07 schema directly in Node.js, Python, or Go validation middleware to enforce data contracts at API boundaries and prevent malformed payloads from reaching your database.
TypeScript Type Generation
Use the generated JSON Schema as input to tools like json-schema-to-typescript or quicktype to automatically produce TypeScript interfaces and types. Start from a real JSON payload and end up with accurate, strongly-typed interfaces without writing them by hand.
Database Schema Design
Generate schemas from MongoDB documents or DynamoDB item exports to understand the shape of your data before designing indexes or migrating to a relational database. The inferred required fields and types give you a starting point for column definitions and constraints.
Form Builder Configuration
Generate JSON Schemas to drive dynamic form builders like react-jsonschema-form or JSON Forms. Add description placeholders using the option in the generator, then fill them in to create human-readable labels and help text for each field in your form.
Data Contract Testing
Capture the schema of a known-good API response and use it as a contract in consumer-driven contract tests with Pact or similar frameworks. Detect breaking changes when a provider removes a required field or changes a property type between releases.
The JSON Schema Generator analyses a JSON payload and produces a complete, standards-compliant JSON Schema document entirely in your browser. It supports both JSON Schema Draft-07 — the most widely deployed version, supported by AJV, jsonschema, and most OpenAPI tooling — and the modern Draft 2020-12 specification used by newer validators and code generators. No data is ever sent to a server.
Type Inference
The generator traverses every value in the input document and maps it to the correct JSON Schema type. JSON strings become "type": "string", integers become "type": "integer", floating-point numbers become "type": "number", booleans become "type": "boolean", and null values become "type": "null". Nested objects are recursively processed into properties sub-schemas, and arrays are analysed to produce an items schema.
Required Field Inference
When the "Infer Required Fields" option is enabled, the generator adds a required array to each object schema containing every key whose value is not null. For arrays of objects with the "Merge Array Item Schemas" option enabled, a key is only marked required if it appears in every item in the array, giving you a conservative required set that reflects the actual data rather than a single sample.
String Format Detection
The generator recognises six common string formats automatically. ISO 8601 date-time strings like 2024-03-15T10:30:00Z are annotated with format: date-time. Plain dates like 2024-03-15 receive format: date. Email addresses, HTTP/HTTPS URIs, UUID v4 strings, and IPv4 addresses are each detected and annotated with their respective format keywords. Disable this option if you need all strings to remain unannotated.
Array Item Schema Merging
When an array contains multiple objects, the "Merge Array Item Schemas" option combines all item schemas into a single representative schema. Properties that appear in every item are marked required; properties that appear in only some items are included but not required. This produces a more accurate items schema than using only the first element, especially for heterogeneous arrays from real API responses.
Draft-07 vs Draft 2020-12
Draft-07 uses the URI http://json-schema.org/draft-07/schema# and is the safest choice for maximum compatibility with existing validators, OpenAPI 3.0 tooling, and code generators. Draft 2020-12 uses the HTTPS URI https://json-schema.org/draft/2020-12/schema and introduces cleaner semantics for $ref, unevaluatedProperties, and prefix items. Choose 2020-12 when targeting AJV 8+, the TypeScript json-schema-to-typescript v12+ toolchain, or any validator that explicitly supports the latest specification.
Description Placeholders
Enabling "Add Description Placeholders" inserts an empty description string on every property and object schema. This is useful when you plan to use the generated schema as a starting point for API documentation or a form builder configuration — you can fill in the descriptions without having to add the keys manually to every property.
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Frequently Asked Questions About JSON Schema Generator
A JSON Schema is a vocabulary that describes the structure, types, and constraints of a JSON document. It is used for runtime validation, API documentation in OpenAPI specs, TypeScript type generation, and form builder configuration. This JSON Schema generator creates one automatically from any existing JSON payload.
Draft-07 is the most widely supported version, compatible with AJV, jsonschema, and OpenAPI 3.0 tooling. Draft 2020-12 is the latest specification with cleaner $ref semantics and new keywords like unevaluatedProperties. Choose Draft-07 for maximum compatibility and Draft 2020-12 when targeting modern validators like AJV 8+.
When "Infer Required Fields" is enabled, every property whose value is not null is added to the required array. For arrays of objects with merging enabled, a field is only marked required if it appears in every item in the array. This gives a conservative required set that reflects the actual data rather than a single sample.
The generator detects six formats: date-time (ISO 8601 with time), date (ISO 8601 date only), email addresses, HTTP/HTTPS URIs, UUID v4 strings, and IPv4 addresses. Each is annotated with the corresponding JSON Schema format keyword. Disable "Detect String Formats" if you need all strings to remain unannotated.
When enabled, the generator combines the schemas of all objects in an array into a single representative items schema. Properties present in every item are marked required; properties in only some items are included but optional. This produces a more accurate schema than using only the first array element.
Yes. The generated Draft-07 schema is immediately usable with AJV, jsonschema (Python), and most other validators. Copy the output, save it as a .json file, and pass it to your validator. For AJV 8+ you can also use the Draft 2020-12 output by selecting that option before generating.
Completely. All schema generation runs locally in your browser with no server uploads. Your JSON payloads, API responses, and database records never leave your device. This makes the tool safe for sensitive business data, credentials, and any proprietary JSON structures you need to document.