JSON Schema from Sample

Frequently Asked Questions

Which JSON Schema draft does it output?

Draft 2020-12, the current draft. It's supported by Ajv 8+, jsonschema (Python), and most modern validators. If you need an older draft (draft-07 is common in legacy tooling), change the <code>$schema</code> URL at the top and validate — most of the syntax is backward-compatible.

Does it infer format for strings?

Yes, when the string clearly matches a known format. Dates become <code>format: date-time</code>, emails become <code>format: email</code>, URIs become <code>format: uri</code>, UUIDs become <code>format: uuid</code>. Ambiguous strings stay untyped so validators don't reject legitimate values.

How are required fields determined?

Any key present in the sample is marked required. This is the safest default — if you want a field to be optional, remove it from the <code>required</code> array. For schemas built from multiple sample objects, merge the required arrays manually or use a library like quicktype.

Can I use this for OpenAPI schemas?

Yes. OpenAPI 3.1 uses JSON Schema 2020-12 under the hood, so the output drops directly into an OpenAPI <code>components/schemas</code> section. For OpenAPI 3.0 (which uses an older subset), you may need to drop a few 2020-12-specific keywords.