Online JSON Schema generator: paste JSON data and automatically generate the corresponding JSON Schema definition. Supports nested objects, arrays, type inference, runs locally in browser.
TL;DR: Free online JSON Schema generator. Paste JSON and automatically generate the corresponding JSON Schema definition with nested object and array support and type inference. Runs locally in your browser, no registration.
For local tools, open DevTools → Network and search your input — it should not appear in requests.
Next steps
Usage Guide
Infer JSON Schema drafts from samples, then tighten before production.
1. Generate
Paste representative JSON, pick draft-07 or 2020-12, optionally detect formats.
2. Edit
Fix required/bounds/enums; inference only saw the sample.
3. Draft choice
Align with production validators, not novelty.
4. Toolchain
Generate → edit → validate with pos/neg cases in CI.
5. Sample bias
Include failures, empties, and nulls when real.
6. Formats
Heuristics need enforcement plugins to matter.
FAQ
Nowhere. Generation happens entirely in your browser — there is no account system and no usage quota.
It recognizes string, integer, number, boolean, null, object, and array: objects yield properties and required, arrays infer items from the first element. An empty array only gets its type declared as array, and heterogeneous arrays are best finished by hand.
Both are available. Draft-07 has the widest ecosystem; 2020-12 fits newer toolchains (e.g., prefixItems). Align with the $schema your production stack already uses rather than chasing the newer number — the same schema may not behave identically across validators.
Only when you want email or URI hints. Detection is heuristic and can mislabel test inboxes, intranet URIs, or custom IDs — treat hits as clues, not contracts. The constraints also stay inert until the downstream validator enables format checking (e.g., ajv-formats).
No. Inference only describes shapes it has seen: required needs manual tightening, minLength/pattern/minimum must be added by hand, and enums should only be written once the business confirms the set is closed. Record the refinements in your PR so nobody freezes the draft as the final version.
Don't paste only the happy path. Include error bodies, empty arrays, and explicit nulls, or the generated schema stays blind to them; when samples diverge, merge several of them or hand-write oneOf/anyOf. The coverage of your samples caps the quality of the schema.
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