Document an API payload
Create an initial schema while documenting an existing request, response or event format.
100% local · files never leave your browser
Generate tool
JSON Schema Generator
Generate a practical JSON Schema from sample JSON locally in your browser. Review inferred types and required fields before use.
✓ Free to use✓ No signup✓ Runs locally
160 bytes · local only
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Processed entirely in this tab
Your input and result are not sent to JSON Hearth or stored on a server.
When to use it
What Schema Generator helps you do
Schema inference turns a representative JSON example into a starting contract. It can save time, but the result should be reviewed against real business rules.
Bootstrap validation
Generate a first draft before adding required fields, ranges, patterns and descriptions manually.
Understand sample data
Summarize nested types and properties in a machine-readable form.
How it works
Schema Generator, without the upload.
Add your data
Paste a value, open a local file or begin with the working sample.
Run the tool
The transformation executes in your browser, not on our servers.
Review the result
Check the output, then copy or download it for your next task.
Important limitations
What to check before using the result
Review required
One example cannot reveal every optional field, allowed value or future variation.
Review required
Inferred required fields and types must be reviewed before production validation.
Common questions
About Schema Generator
Does JSON Schema Generator upload my data?
No. Your input is processed by code running in your browser and is not sent to an application server.
Is Schema Generator free to use?
Yes. The tool is free, requires no account and can be used directly in the browser.
Is an inferred JSON Schema production-ready?
Treat it as a draft. Add domain rules and test it against multiple valid and invalid examples.
Can the generator detect optional fields?
A single sample cannot reliably distinguish optional fields from fields that simply happened to be present.