{ } How to use

Paste a flat JSON object whose keys are paths, such as a.b.c.
Set the delimiter to the one your keys use.
Select Process to rebuild the nested document.

{ } How it works

JSON Unflatten works on the text you provide. Adjust the options, then select Process ▸ and it runs entirely in your browser — nothing is uploaded to a server — then shows the result in the Output panel.

Inputs

Flat JSON — paste or type your input in the left panel (use Sample for an example)
Key delimiter — a value (default: ".")

Output

JSON — copy it, download it, or switch the Output panel to Tree view to explore it.

{ } Common uses

Restore the structure after a flattened file has been edited in a spreadsheet.
Turn a dot-notation configuration export back into nested JSON.
Rebuild a translation file that was flattened for review.

{ } Limitations

The input must be a flat JSON object. An array, or a bare value, is rejected.
Numeric segments become object keys — items.0 rebuilds as a key named 0, not as an array — so a flatten-then-unflatten round trip returns objects where the original had lists.
When one key is a prefix of another, such as a.b alongside a.b.c, the later key overwrites what the earlier one built.

{ } FAQ

Is my data uploaded to a server?

No. Everything runs locally in your browser — your files never leave your device.

Can I process more than one file at once?

This tool works on one input at a time.

Is this tool free?

Yes — it’s completely free and needs no sign-up.

Why did my array come back as an object?

A path carries no type, so items.0 can only be rebuilt as a key called 0. Convert those objects back to arrays yourself where you need real lists.

Do the values have to be strings?

No. Any JSON value is placed at its path unchanged — numbers, booleans, and whole nested objects and arrays all survive.