JSON Unflatten

flat dot or bracket keys → nested objects

Reverse of json-flatten: turn { "user.address.city": "..." } back into a nested object. Configurable delimiter / style.

Key style

Input flat JSON

Nested output

Paste flat JSON.

How to unflatten

Paste your JSON in either panel.
Configure Style: Dot (user.address.city), Bracket (user[address][city]), or Custom delimiter.
Toggle Flatten arrays — on (items.0.id) or off (arrays kept whole).
The opposite panel updates live. Copy or Download.

What if some keys aren't dotted?

They stay at the top level, alongside the un-flattened nested keys.

What about numeric path segments?

Numeric segments are treated as object keys, not array indices. If you need array reconstruction, switch to bracket style.

Will it work offline?

Yes.