Prepare tabular data
Turn nested values into path-based columns for exports and quick inspection.
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Convert tool
Flatten or Unflatten JSON
Flatten nested JSON into dot paths or rebuild nested JSON from flat keys locally in your browser.
✓ Free to use✓ No signup✓ Runs locally
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Processed entirely in this tab
Your input and result are not sent to JSON Hearth or stored on a server.
When to use it
What Flatten JSON helps you do
Flattening converts nested paths into simple keys, while unflattening reconstructs objects from those paths. Use this implementation for object-shaped data; arrays and empty containers do not round-trip intact.
Compare configurations
Represent deeply nested settings as a flat list of keys and values.
Rebuild nested objects
Convert dot-path keys back into objects when importing flat configuration data.
Important limitations
What to check before using the result
- Keys that already contain separator characters can be ambiguous without an agreed escaping convention.
- Array indexes become numeric dot-path segments, but unflattening creates object properties rather than restoring arrays.
- Flattening omits empty objects and empty arrays. Keep the source and avoid this transform when those shapes must be preserved.
Common questions
About Flatten JSON
What is a flattened JSON path?
It is a key such as user.address.city that represents a value nested inside several objects.
Can flattening always be reversed?
No. This implementation loses empty containers and reconstructs array indexes as object keys. Round trips are limited to non-empty nested objects with unambiguous, non-conflicting dot paths. Compare the result with the source before replacing it.