JSON Schema Mapper

The JSON Schema Mapper lets you visually map fields between two JSON structures. Paste a source and target JSON, then click fields on each side to create mapping connections. You can configure transformations like direct copy, rename, type casting, or template expressions. The tool then generates transformation code in JavaScript, TypeScript, Python, or jq — ready to use in your project.

Five transformation types are supported: Direct (copy value as-is), Rename (just changes the field name), Type Cast (converts between string, number, boolean, and other types), Template (combine multiple fields using expressions like "${firstName} ${lastName}"), and Custom (write your own transformation function body). Each mapping line is color-coded by transformation type.

The tool generates transformation code in four languages: JavaScript and TypeScript (using a transform function with dot-path access), Python (using a def transform function with dict access), and jq (using a jq filter expression). The generated code handles nested field access and all configured transformations.

Yes. Both the source and target JSON trees support nested objects and arrays. You can expand and collapse tree nodes to navigate deep structures. Mappings work with any depth level — for example, mapping "source.user.address.city" to "target.location.city" is fully supported.

When you click a source field and then a target field, a curved line appears connecting them. Lines are color-coded: green for direct copy, blue for rename or transform, orange for type cast, and purple for template or custom transformations. On mobile devices, mappings are shown as a text list instead of visual lines for better usability.

Yes. You can export your mapping configuration as a JSON file that includes all source-to-target field mappings and their transformation rules. Import a previously exported configuration to restore your mappings instantly. This is useful for sharing mappings with your team or reusing them across projects.

No. All JSON parsing, tree rendering, mapping, and code generation happen entirely in your browser using JavaScript. Your schemas and data never leave your device — no server calls, no uploads, no data collection. This is critical for developers working with production schemas or sensitive data structures. Verify this in your browser DevTools Network tab.

Common use cases include API response transformation (mapping REST API responses to your frontend model), data migration (mapping old database schema to new schema), ETL pipelines (mapping source data format to target format), API version upgrades (mapping v1 response to v2 format), and integration work (mapping between different third-party API formats). The visual approach makes these mappings much easier to understand and maintain.