Free CSV to JSON Schema Converter — infer a validation schema from CSV columns in your browser

What Is CSV to JSON Schema Conversion?

CSV to JSON Schema conversion derives a JSON Schema that describes and validates the rows of a CSV file. Each column header becomes a property, and the converter infers each property type from the column values — numeric columns become "type": "number", true/false columns become "boolean", and the rest become "string". The result is a reusable contract you can use to validate data, document an API, or seed an OpenAPI definition.

How Type Inference Works

CSV cells are untyped text, so the tool scans all rows of each column and assigns the narrowest fitting JSON Schema type:

  • number — every non-empty value in the column is numeric.
  • boolean — every value is true or false (any case).
  • string — the fallback for mixed, text, or empty columns.

How to Use the CSV to JSON Schema Converter

  • Paste CSV with a header row into the input, or load the example.
  • Click Convert to Schema to generate the JSON Schema.
  • Copy it into your validator, API contract, or OpenAPI document.

Common Use Cases

Validate incoming CSV uploads against a schema, document the structure of a dataset, generate the properties block of an OpenAPI model, or enforce a data contract in an ETL pipeline — all in your browser, with nothing uploaded.

Frequently Asked Questions

Does it infer property types or mark everything as string?

It infers types. Each property is typed number, boolean, or string based on every value in the column.

Does the schema describe a row or the whole file?

It describes a single row object. To validate the full file, wrap the generated object schema in an array schema ("type": "array" with items set to this schema).

Which JSON Schema draft does it use?

It emits a standard object schema with a properties map and inferred type values, compatible with common validators; adjust the $schema draft to your tooling if needed.

Is my CSV uploaded to a server?

No. Conversion runs entirely in your browser — your data never leaves your device.