JSON Schema Generator

The JSON Schema Generator turns sample JSON into a validator-ready schema for APIs, webhooks, configuration files, data pipelines, and documentation. Paste a representative JSON object, array, or NDJSON feed, choose the inference style, and the tool builds a schema with nested properties, array item rules, nullable values, examples, and readable path-by-path notes.

Why Use a Sample-Based JSON Schema Generator?

Writing JSON Schema by hand is precise but slow, especially when the data contains nested objects, arrays of records, optional fields, and nullable values. This generator gives you a structured first draft that captures the observed shape of your JSON data, then highlights where human review is still needed. It is useful for API request validation, response contracts, OpenAPI work, webhook payloads, event streams, and configuration schemas.

How to Use

1. Paste a representative JSON object, JSON array, or newline-delimited JSON records into the sample editor.
2. Select the JSON Schema draft and decide whether to infer required fields, examples, enum hints, string formats, and closed objects. By default, the draft is Draft 2020-12, required fields are set to Observed in every object, Detect formats, Include examples, and Infer enum hints are on, and Closed objects is off. The schema title starts as GeneratedSchema.
3. Click Generate JSON Schema to infer types, nested properties, array items, nullable fields, and validation hints.
4. Check the generated map to see each path, inferred type, required status, format, and rule before using the schema.
5. Copy the generated schema and refine domain-specific validation rules such as exact ranges, ID patterns, and business-specific enums.

What the Generator Infers

• Core JSON types: object, array, string, number, integer, boolean, and null.
• Nested object properties and required fields based on what appears in every observed object.
• Array item schemas by merging the observed items in the sample.
• Common string formats including email, URL, date, date-time, UUID, IPv4, and IPv6.
• Optional examples, enum hints, observed numeric ranges, and observed string lengths.

FAQ

What does this JSON Schema Generator do?

It reads sample JSON and creates a JSON Schema that describes the observed data shape. The generator infers object properties, arrays, primitive types, nullable values, examples, enum hints, required fields, and common string formats.

Can a generated schema be used in production immediately?

Use it as a strong starting point, then review it. Sample data cannot know every business rule, so you may still need to add patterns, exact ranges, allowed enum values, version rules, and stricter additionalProperties settings.

Which JSON Schema drafts are supported?

The tool can generate schemas for Draft 2020-12, Draft 2019-09, and Draft-07 by setting the $schema URI. The inferred structure is intentionally compatible with common validators.

How are required fields inferred?

When required inference is enabled, a property is marked required only when it appears in every observed object at that level. For an array of objects, this means the field must appear in every sampled item.

Does the tool support arrays of objects and NDJSON?

Yes. A top-level JSON array is treated as an array schema, and newline-delimited JSON records are treated as an array of records. Item properties are merged from the observed samples.