What does this tool do?
JSON Schema Generator produces a validating JSON Schema from a sample JSON document. For developers documenting APIs, validating incoming data, or writing contract tests, it removes the tedium of hand-writing schemas, and it supports the draft-07, 2019-09, and 2020-12 versions.
How to use it
- Enter your configuration details.
- Review the generated output.
- Copy the ready-to-use code or file.
Inferring types and structure
The tool walks your data and assigns a type to every field: whole numbers become integer, decimals become number, true/false become boolean, and text becomes string. For objects it builds a properties block and adds additionalProperties: false so unexpected fields are rejected. Arrays get an items schema inferred from the first element; empty arrays allow any item. Starting from a single example, you end up with a working validation schema you can refine.
Required fields and draft version
When 'Mark all fields as required' is on, every key of each object is added to its required array, so the schema enforces that all fields are present. If your payload has optional fields, turn this off and edit the generated schema by hand. You can choose among three draft versions; this only changes the $schema URI and syntax conventions, while the inferred structure stays the same.
Frequently asked questions
Which JSON Schema drafts are supported?
draft-07, 2019-09, and 2020-12. Your choice only changes the output's $schema URI; field types and structure are inferred the same way across all versions.
Why is additionalProperties set to false?
To make the schema strict: extra, undefined fields are rejected. If you want to allow additional fields, remove that line from the generated schema or set it to true.
Does the inferred schema cover every case?
The schema is based on the example you provide; constraints like format, minimum/maximum, or enum are not added automatically. You can add them yourself to tighten validation.
Is JSON Schema Generator free?
Yes. JSON Schema Generator and all 300+ tools on MagmaNex are completely free with no signup or account required.
Is my data safe?
Yes. Everything runs locally in your browser. The data you enter is never sent to a server, stored, or shared.
Does it work on mobile?
Yes. JSON Schema Generator works on phones, tablets and desktops — no app download needed.
🔒 Privacy: everything runs in your browser, your data is never sent to a server.