JSON Parser
Online JSON Parser
OnlinePaste a flat JSON object with dot-notation keys and click Unflatten. The tool reconstructs the nested object — {"address.city": "London"} becomes {"address": {"city": "London"}}. Use it to reverse the output of the Flatten JSON tool, or to expand flat key-value configs into structured JSON.
Free, fast, runs in your browser. No login needed.
.).The unflattener splits each key by the separator character and follows the resulting path to build a nested object. For example, the key user.address.city with separator . produces {"user": {"address": {"city": "..."}}}.
Separator must match. Use the same separator that was used when the object was flattened. If the original separator was __ or /, enter that in the separator field before unflattening.
Arrays are not reconstructed. If the flat object was produced from an array (with keys like items.0, items.1), those numbered keys will produce a nested object with string keys "0", "1" — not a proper JSON array. The Flatten JSON tool preserves arrays as-is, so this situation only arises if the flat input was produced by a different tool.
Path conflicts. If two keys share a path prefix where one extends further (e.g., a and a.b), the intermediate path is overwritten. The last key processed wins.
The Flatten JSON tool. Use the same separator in both directions to round-trip your data correctly.
Unflattening will split on every occurrence of the separator, including those inside original key names. Use a separator that does not appear in your key names, or switch to a different separator in both the flatten and unflatten steps.
No. Numeric path segments produce objects with string keys ("0", "1", ...) — not JSON arrays. The Flatten JSON tool on this site preserves arrays as values, so this is only an issue with flat data from external sources.
No. Unflattening runs entirely in your browser.