JSON Unflatten
Restore nested JSON from flat dot-notation keys. Merge flattened objects back into hierarchical structures in your browser.
Restore Nested JSON from Flat Keys
Analytics exports, form builders, and NoSQL flattening utilities often produce JSON where hierarchy is encoded in key names, such as user.address.city. This tool rebuilds the nested structure so you can work with familiar objects again.
Custom Separators and Arrays
Choose the separator that matches your source data (dot, underscore, or slash). Numeric path segments become array indexes, so keys like items.0.id expand into items[0].id in the restored JSON.
If you need the opposite transformation, flatten objects with the Flatten JSON Object tool or format results using the JSON Formatter.
Frequently Asked Questions
What input shape is required?
Provide a single JSON object whose keys are flat strings. Values can be strings, numbers, booleans, or null.
Can I unflatten underscore-separated keys?
Yes. Set the separator to _ when your keys look like server_host instead of server.host.
What if two keys conflict?
The last key processed wins when paths collide. Review the flat source when merges look unexpected.
Does it validate JSON syntax?
Yes. Invalid JSON is rejected with a clear error before unflattening begins.
Is data sent to a server?
No. Unflattening happens entirely in your browser.
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