JSON to TS

THE PRACTICAL GUIDE · NORMANDIN SYSTEMS

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JSON to TS converts JSON sample data to TypeScript. The tool infers interface properties from the values and structure visible in a sample. Inference provides a useful starting point, but one sample cannot describe every valid future record. TypeScript interfaces describe compile-time shape and are erased at runtime. Validate untrusted incoming JSON separately when runtime checks are required. Include null values, empty collections, optional fields, and several representative records when reviewing the inferred structure. Compile or validate the generated draft in the target project. Use the worked example to understand what a successful result looks like, then compare it with a small sample of your own input. Keep the original available until you have checked the output in its destination. Conversion establishes a representation; it does not establish that the underlying information is correct or that the receiving application accepts every supported feature.

Guide updated October 13, 2026

How to use this tool

1. Enter or load JSON sample data using the input controls. Begin with the worked example or a small sample for which you know the expected result.
2. Review any available conversion options, then inspect the TypeScript result. Resolve a reported parse error at its source before attempting to reuse the output.
3. Check the example below against your own data. Include null values, empty collections, optional fields, and several representative records when reviewing the inferred structure. Compile or validate the generated draft in the target project.
4. Copy or save the resulting TypeScript content using the controls provided, then validate it in the application or parser that will actually consume it.

SEE IT IN PRACTICE

A worked example

{"name":"Ada","score":10,"active":true}

interface DataProps { name: string; score: number; active: boolean; }

The example supplies a string, a number, and a boolean. These give the generator evidence for three different interface properties; exact names and formatting follow the tool options.

Optional properties and unions

A field absent from some records may require an optional marker, while a field whose values legitimately vary can require a union type. A single complete example cannot reveal either condition. Review several representative records and the API contract before accepting the inferred interface. Keep an explicit null distinct from an absent property when downstream code treats them differently.

Interfaces are erased at runtime

The generated TypeScript interface helps the compiler check code, but it does not validate an HTTP response after the program runs. A value can be asserted to match an interface without actually matching it. If the boundary requires validation, add a runtime check using the application’s chosen approach. Review optional properties and unions explicitly, because a sample containing one non-null value cannot establish all valid future alternatives.

When this tool is useful

• Prepare TypeScript models for API responses while retaining a separate copy of the source.
• Use a small example to troubleshoot field-type and nesting assumptions and identify a representation mismatch.
• Create TypeScript scaffolding for application code without manually rewriting every field or symbol.

Tips for a better result

• TypeScript interfaces describe compile-time shape and are erased at runtime. Validate untrusted incoming JSON separately when runtime checks are required.
• Include null values, empty collections, optional fields, and several representative records when reviewing the inferred structure. Compile or validate the generated draft in the target project.
• After changing formats, compare meaningful values rather than whitespace alone. Read the TypeScript output with its intended parser when exact types or escaping matter.

Frequently asked questions