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Convert a JSON Schema into an OpenAPI 3.0 Schema Object, adjusting type arrays, nullable and unsupported keywords.
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This conversion runs entirely in your browser — your input never leaves your device.
JSON Schema to OpenAPI Schema is a free online converter on AltFTool that converts a JSON Schema into an OpenAPI 3.0 Schema Object, adjusting type arrays, nullable and unsupported keywords — no signup and nothing to install.
The conversion runs entirely in your browser: the JSON Schema you paste is converted on your own device and is never uploaded to AltFTool. JSON Schema to OpenAPI Schema is powered by the @openapi-contrib/json-schema-to-openapi-schema library, and the OpenAPI Schema result can be copied or downloaded as json-schema-to-openapi-schema.json.
The input is a JSON Schema document rather than raw data — the converter reads the schema's declared types and constraints, not an example payload.
| Input format | JSON Schema (JSON syntax) |
|---|---|
| Output format | OpenAPI Schema (JSON syntax) |
| Output file | json-schema-to-openapi-schema.json (application/json) |
| Runs | In your browser — the input is not uploaded. |
| Library | @openapi-contrib/json-schema-to-openapi-schema |
| Category | JSON Schema converters on AltFTool |
Open JSON Schema to OpenAPI Schema on AltFTool — the converter loads straight away, with no account.
Paste your JSON Schema into the left-hand input pane, or press Sample to load a working example.
The conversion runs automatically about 300ms after you stop typing — there is no Convert button, and nothing is uploaded while it works.
If this converter exposes options, open Settings to change them — the output re-runs as you adjust.
Copy the OpenAPI Schema output with the Copy button, or download it as json-schema-to-openapi-schema.json.
No. JSON Schema to OpenAPI Schema runs entirely in your browser using the @openapi-contrib/json-schema-to-openapi-schema library, so the JSON Schema you paste is converted on your own device and never reaches AltFTool's server.
The @openapi-contrib/json-schema-to-openapi-schema library, running in your browser. The OpenAPI Schema you see is that library's output rather than an approximation written here.
There is no server-side limit, because nothing is uploaded — JSON Schema to OpenAPI Schema converts in your browser, so the practical ceiling is your own device's memory.
The result is OpenAPI Schema. Copy it from the output pane in one click, or download it as json-schema-to-openapi-schema.json — AltFTool names the file after the converter and serves it as application/json.
Yes. JSON Schema to OpenAPI Schema is free to use on AltFTool, with no account and no sign-up.
Drop the live JSON Schema to OpenAPI Schema workspace into your own docs page, tutorial or blog post with one snippet. Free, responsive, light and dark — just keep the “Widget by AltFTool” credit link visible.
<iframe src="https://www.altftool.com/embed/widget/transform/json-schema-to-openapi-schema"
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<p style="font-size:12px;margin:4px 0 0">Widget by <a href="https://www.altftool.com/transform/json-schema-to-openapi-schema?utm_source=embed&utm_medium=widget" rel="nofollow">AltFTool — free online tools</a></p>More of AltFTool's JSON Schema and format tooling, and the guides around it.