Unflatten JSON

Rebuild nested JSON from a flat object whose keys use dot notation, such as user.name or user.roles[0].

Example:

Flat JSON

How it works

Did you receive a tabular export (from a spreadsheet or a database) whose columns are named with paths like address.city or tags[0], and you need to rebuild nested JSON an application can use? Paste the flat object: each key is split into segments (at the dots and index brackets) to automatically rebuild the corresponding nested objects and arrays.

What happens if the input is not a flat JSON object?

A clear error is shown: the tool expects a top-level JSON object (not an array or a simple value) whose keys describe paths.

Is this operation reversible?

Yes, use the "Flatten JSON" tool on the result obtained here to get back the original flat object.

<strong>100% local processing:</strong> rebuilding runs entirely in your browser via WebAssembly — your JSON data never leaves your device.