Formalint

Schema design

JSON Schema Generator

Generate a JSON Schema from a sample payload, infer object properties, required fields and array item shapes, then run basic validation locally.

Read schema guide Open JSON formatter

Sample JSON

0 bytes

Schema

Ready

Generated schemas are inferred from examples. Review required fields, nullable values and business rules before using them in production.
JSON FormatterFormat and inspect payloads JSON GuideRead payload review notes Safe Tool UsageSanitize samples before pasting

Reference notes

JSON Schema from real examples

Inference limits

A sample payload can reveal observed fields and types, but it cannot know every valid business rule. Treat the result as a strong draft.

Array merging

The generator compares array items and builds a shared item schema so mixed examples produce a broader but still readable schema.

Local processing

Sample JSON and generated schema output are handled in the browser. Formalint does not upload pasted payloads to a backend.