JSON Unflatten
Flatten JSON online then unflatten back to nested objects and arrays. Free browser tool, no upload, no account. Rebuild nested JSON locally.
Runs locally in your browser. Your input is not uploaded to DevToolMate servers.
Developer Quick Tips
- Paste flat dotted-key JSON (e.g., {"user.name": "Alice", "user.roles.0": "admin"}) to rebuild nested structure instantly.
- Numeric path segments auto-convert to array indexes; no manual array syntax needed.
- Round-trip workflow: flatten nested JSON, edit in a spreadsheet, then unflatten back to nested form.
- Use the output to rebuild API fixtures or convert flat analytics exports back to nested payloads.
- Output downloads as nested.json and is ready for JSON formatter or validator tools.
Frequently asked questions
What are dotted keys and how does JSON Unflatten use them?
Dotted keys represent nested paths as flat strings. For example, {"user.name": "Alice", "user.roles.0": "admin"} unflatten to {"user": {"name": "Alice", "roles": ["admin"]}}. Numeric segments become array indexes. This is useful when you flatten nested JSON to a spreadsheet, edit the flat keys, and need to rebuild the nested structure.
How do I flatten JSON online and then unflatten it back?
Use JSON Flatten to convert nested JSON to dotted-key format. Edit the flat keys in a spreadsheet or text editor. Then paste the result into JSON Unflatten to rebuild the nested structure. This round-trip workflow is common for data transformation and API fixture management.
Does JSON Unflatten upload my data to servers?
No. JSON Unflatten runs locally in your browser. Your input is not uploaded to our servers for processing. All work stays on your device.
Can I use JSON Unflatten to validate or format JSON?
JSON Unflatten focuses on unflattening dotted keys to nested structure. For validation and formatting, pair it with JSON Validator or JSON Formatter tools. Unflatten outputs pretty-printed JSON ready for those tools.
Is JSON Unflatten free and does it require an account?
Yes. JSON Unflatten is free to use with no account required. Processing stays on your device for the current session.
Will my input be stored after I close the tab?
No. Input stays in memory for the current page. Closing the tab clears it. Theme preference is stored locally in your browser and is not tool input.
Related tools
- JSON Flatten: Flatten JSON online free with dotted keys. Convert nested objects and arrays to dot notation in your browser. No upload, no account, no server processing.
- JSON Formatter: Online JSON formatter - beautify and format JSON in your browser with adjustable indentation and key sorting. Free, no upload, no account.