What does a JSON flattener do?

A JSON flattener converts a deeply nested JSON object into a single-level object where nested keys are combined using a delimiter (usually a dot). For example, {"user":{"name":"Alice"}} becomes {"user.name":"Alice"}. This is useful when working with configuration files, databases that store flat records, or APIs that expect flat query parameters.

What is dot-notation JSON?

Dot-notation JSON is a flat representation of a nested JSON object where each nested key path is joined by dots. For example, the nested path user → address → city becomes the flat key "user.address.city". It is widely used in MongoDB queries, environment variable naming, and configuration systems.

Can I unflatten JSON back to nested?

Yes. Switch to the Unflatten tab and paste flat dot-notation JSON. The tool will reconstruct the original nested structure. For example, {"user.name":"Alice","user.age":30} becomes {"user":{"name":"Alice","age":30}}.

Can I change the delimiter used for flattening?

Yes. By default the tool uses a dot (.) as the delimiter, but you can change it to any character — underscore (_), slash (/), or anything else — using the Delimiter option above the output panel.

Is my JSON data sent to a server?

No. All processing happens entirely in your browser using JavaScript. Your JSON never leaves your device, making this tool safe to use with sensitive configuration data or API responses.

Does it handle arrays in nested JSON?

Yes. Arrays are flattened using bracket-style index keys. For example, {"items":["a","b"]} becomes {"items[0]":"a","items[1]":"b"}. This keeps array indices unambiguous and easy to reconstruct.

Free JSON Utility

Flatten & Unflatten
JSON in Seconds

Transform deeply nested JSON objects into flat dot-notation key-value pairs — or reverse the process. Perfect for config files, API responses, and form data. 100% client-side, no data leaves your browser.

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Instant Flattening

Convert any nested JSON object into flat dot-notation keys in real time as you type.

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Bidirectional

Flatten nested JSON or unflatten dot-notation keys back to nested objects with one click.

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Custom Delimiter

Choose your separator: dot (user.name), underscore (user_name), or any custom character.

Delimiter:

Nested JSONInput

Flat JSON (dot-notation)

Output will appear here…

Frequently Asked Questions

Everything you need to know about JSON Flattener.