JSON Schema Generator

A JSON Schema generator infers a JSON Schema — a formal description of a document's structure, types, and required fields — directly from a real sample of JSON, such as an API response or a config file. Instead of hand-writing every type, properties, and required entry, you paste an example and get a draft schema back instantly.

This tool walks your sample recursively: every key gets a type (string, number, integer, boolean, object, array, or null), nested objects become nested properties, and arrays are inferred from the union of shapes across every item they contain — so an array of objects with slightly different fields still produces one accurate items schema.

The generated schema is a starting point, not a final contract. Keys observed in your sample are marked required by default (turn this off with the Require observed keys toggle if your sample doesn't cover every optional field), and you should review types like numeric strings or date formats that JSON Schema alone can't distinguish from plain text.

Choose between Draft-07 and 2020-12 for the $schema declaration depending on which validator or tool you're targeting. Everything runs locally in your browser — your JSON is never uploaded to a server.

Both are versions of the JSON Schema specification, identified by the $schema URI at the top of the document. For the kind of schema this tool generates — type, properties, required, and a single-shape items — the two drafts behave identically, so switching the Draft selector only changes that one line. The differences that do exist between them show up in more advanced schemas than a generated draft typically needs:

• Tuple arrays. Draft-07 validates a fixed-position array (e.g. [string, number]) with an array of schemas in items. 2020-12 moved that to a dedicated prefixItems keyword and reserves items for constraining any remaining elements — irrelevant here since this tool only ever produces a single items schema shared by every element.
• Recursive references. Draft-07 uses $recursiveRef / $recursiveAnchor for self-referencing schemas; 2020-12 replaced them with the more flexible $dynamicRef / $dynamicAnchor.
• Vocabularies. 2020-12 splits the specification into separate vocabularies (core, validation, applicator, and so on) that a schema can declare support for, instead of Draft-07's single monolithic meta-schema.
• unevaluatedProperties / unevaluatedItems. Introduced after Draft-07 (in draft 2019-09) and refined in 2020-12, these keywords constrain properties or items left unmatched by allOf/if-then-else composition — a feature this tool's output doesn't use.

In practice: pick Draft-07 if you're targeting an older validator, tool, or ecosystem (it's still the most widely supported draft across languages). Pick 2020-12 — the current version of the specification — for new projects, especially if you expect the schema to grow into tuple validation or recursive structures later.