JSON Unflatten
JSON Unflatten is a free online transformer that helps you expand a flat dot/bracket-keyed object back into nested JSON; numeric keys become array indices. JSON Unflatten uses 1 input field, returns 1 output value, and runs in your browser on the device.
Key facts
- Inputs
- 1 field: Flat JSON
- Outputs
- 1 value: Nested
- Runtime
- your browser on the device
- Mode
- Transformer
- Privacy
- Files and text stay in the browser session.
- Cost
- $0, no account required
How to use JSON Unflatten
- 1
Paste or fill in the input
Enter your text or values into the input fields on the page.
- 2
Run the utility
Click Compute to run the utility in your browser and review the result.
- 3
Copy the output
Copy the output value you need from the result panel.
JSON Unflatten details
First, enter Flat JSON in JSON Unflatten. Next, review Nested. Additionally, JSON Unflatten uses 1 input field and 1 output block so the result is easy to scan and copy.
The inverse of JSON Flatten. Paste a flat JSON object whose keys use dot-notation (`a.b.0`) or array brackets (`a.b[0]`) and rebuild the nested structure. Numeric segments are treated as array indices, everything else as object keys. Useful for parsing form-data style payloads, CSV → nested JSON, or undoing a flatten operation. Runs entirely in your browser; free, online, no upload.
Common searches
- json unflatten
- unflatten json
- flat json to nested
- json from dot notation
- expand flat json
- nest json
Related tools
Tools that work with the same formats — most users open one of these next.
JSON Flatten
Flatten a nested JSON document to a single-level object with dot, underscore or bracket paths.
JSON Schema Generator
Infer a JSON Schema (Draft-07) from any JSON document — nested objects and array element types are inferred recursively.
JSON Patch Generator
Generate an RFC 6902 JSON Patch describing the changes needed to turn one JSON document into another.
JSON Sort Keys
Sort the keys of a JSON object alphabetically — recursively, case-insensitively, or with numeric awareness.
JSON to Go Struct
Generate Go structs with json tags from any JSON payload — nested objects become separate named types.
Hex to Binary File
Parse a hex dump or hex string back into a binary file — strips offsets, ASCII columns, prefixes and separators automatically.
Frequently asked
What is JSON Unflatten?
JSON Unflatten is a free online transformer that helps you expand a flat dot/bracket-keyed object back into nested JSON; numeric keys become array indices. JSON Unflatten uses 1 input field, returns 1 output value, and runs in your browser on the device.
What inputs and outputs does JSON Unflatten use?
JSON Unflatten uses 1 input field: Flat JSON. JSON Unflatten returns 1 output value: Nested.
Do my files and data stay private?
Yes. JSON Unflatten runs entirely in your browser using your device's CPU. Files and text are never uploaded to our servers, so your data stays private.
How do I use JSON Unflatten?
Open JSON Unflatten, paste or fill in the input fields, and the result updates instantly. JSON Unflatten runs in your browser with no upload and no waiting.
Which browsers does JSON Unflatten support?
Any modern browser works in Chrome, Firefox, Safari, and Edge on desktop and mobile. JSON Unflatten uses standard web APIs and does not require any plugin, extension, or sign-up.