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# Data mapping transformer

Reshape CSV or JSON rows with per-field rename, cast, default, and lookup rules, then save the whole mapping as portable JSON.

Paste a CSV or JSON array, set the field rules, and the transformed rows appear here.

Every rule runs row by row, in your tab. A value that is missing, empty, or fails its cast falls back to the rule's default and is counted in the facts above, never silently converted. Lookup tables match exact text; a miss either writes the rule's default or leaves the cell empty. The mapping itself is separate from the data: download it and the same rules reshape next month's file. It does not write to databases or APIs; it reshapes rows and nothing more.
Options

## More fake data tools

- [Bulk test data](/data/test-data)
- [Relational datasets](/data/relational)
- [JSON converter](/json/convert)
[All fake data tools](/data)

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