Tiny Toolkit

JSON Unflattener

Restore a flat dot-notation JSON object back to its original nested structure — the reverse of flattening. Paste key-value pairs like {"user.name": "Alice", "user.age": 30} and get back a properly nested object. Useful when working with systems that store or transmit nested data in a flattened form and you need to reconstruct the hierarchy.

All processing happens in your browser. No data is sent to any server.

Frequently Asked Questions

What is JSON unflattening?
Unflattening is the reverse of flattening. It takes a flat object with dot-separated keys like {"a.b.c":1} and reconstructs the nested structure: {"a":{"b":{"c":1}}}.
What separator should I use?
Use the same separator that was used when the JSON was flattened. The default is a dot. If your keys use underscores or slashes as separators, select the matching option.
What happens if a key segment already exists as a non-object value?
If a conflict is detected during reconstruction, the later key path overwrites the earlier value. For best results, ensure all key paths are consistent and non-conflicting.
Can I unflatten JSON that was not created by this tool?
Yes, as long as the input is a valid flat JSON object using a consistent separator character for all keys. The tool is not limited to output from the JSON Flattener.

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