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JSON to TypeScript Interfaces
Generate deterministic TypeScript declarations from one strict JSON sample.
Pasted JSON, One UTF-8 JSON file
generated-types.ts, typescript-inference-report.json
Browser only
Runs locally in your browser. Your files, pasted content and generated output are not uploaded. Reset clears this tool’s working data.
This tool needs JavaScript. If it does not load, refresh the page and try again.
How to use this tool
- Enter one strict JSON sample or select one UTF-8 file.
- Select Generate TypeScript declarations. Root is the fixed root name.
- Download the full declarations and inference report.
Examples
{"id":1,"name":"Alice","tags":["a"]} yields a Root interface with number, string and string[] properties.
Limitations
- At most 1 MiB input, 20 levels, 50,000 parsed values, 10,000 shape visits, 1,000 named object shapes, 5 MiB cumulative signatures and 5 MiB complete output; 30 seconds.
- Arrays retain distinct whole observed shapes; no optional-key merging, date/format inference or runtime decoder.
- All numeric shapes become TypeScript number. Exact or very large JSON values do not acquire a lossless JavaScript runtime representation.
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