JSON unflattener
Processed in your browser · nothing is uploaded
Rebuilds nested JSON from flat dotted-path keys. `user.address.city` becomes an object three levels deep, and `items[0]` becomes an array element.
How to use the json unflattener
This is the direction you need after the data has been through something flat. A CSV export, a form post, a set of environment variables and most analytics payloads all arrive as one level of keys, and the structure the application expects has to be put back.
A path decides the container type it creates: a bracketed number makes an array, a name makes an object. a[0].b produces an array containing one object. That means the same prefix cannot be both; a[0] and a.x in the same input describe a value that is an array and an object at once, and the later key wins rather than the tool guessing.
One practical note about ordering: array indices are filled at the position given, so a flat set that skips an index produces a sparse array with nulls in the gaps. That is faithful to what the keys said, and usually means the flat data lost a row somewhere upstream.
Questions
By the path. A bracketed number makes an array position, a name makes an object key.
It cannot be. The later key wins rather than the tool guessing at what was meant.
The gap is filled with null. That is faithful to the input, and usually means a row went missing upstream.
Not here. The dot is the near-universal convention and mixing conventions is how paths get misread.
No. Everything runs in your browser, which matters when the file holds credentials or customer data.