JSON Unflattener
Rebuild nested JSON from dot-notation keys.
Dot keys back to nested JSON
The inverse of flattening: this reads keys like "a.b.c" and rebuilds the nested object they describe, so a flattened export or spreadsheet row becomes structured JSON again.
It rebuilds structure after a spreadsheet round-trip: edit flattened dot-notation keys in a sheet, then unflatten them back into the nested JSON your application expects.
Pairs with the flattener
Use the same dot convention both directions. The rebuild runs entirely in your browser with nothing uploaded. Your data is rebuilt on your device and never uploaded.
Frequently asked questions
What does this json unflattener do?
Rebuild nested JSON objects from flat dot-notation keys.
What input does it expect?
A flat JSON object with dot-separated keys, such as {"user.name": "Ana", "user.tags.0": "admin"}. That rebuilds to {"user": {"name": "Ana", "tags": ["admin"]}}.
When are arrays created?
When the next part of a key is a number. "items.0.id" creates an items array, while "items.first.id" creates an items object.
What if a key itself contains a dot?
It is split anyway, since dots are always treated as separators. Rename such keys before unflattening if they must stay whole.
Related tools
More free browser utilities for data cleanup, formatting, and developer workflows.