---
title: "JSON Flatten - Flatten Nested JSON Online | CanDoYa"
description: "Flatten nested JSON into dot-path keys instantly. Choose separators and array notation, then copy clean flat JSON. Free, private, and browser-based."
url: https://candoya.com/tools/json-flatten/
locale: en
type: browser-tool
---

# Free JSON Flatten Tool

Category: Developer

## What does a JSON flatten tool do?

A JSON flatten tool converts nested objects and arrays into one-level JSON whose keys contain each value's full path. For example, user.address.city becomes a single key instead of three nested objects. Flat paths are easier to compare, map to spreadsheet columns, store as settings, and inspect in logs.

This converter walks every branch locally in your browser and writes one path for each leaf value. Pick dots, slashes or underscores between object keys, choose bracket or segment notation for array indexes, and format the result as readable or compact JSON. Empty nested objects and arrays stay in the output instead of disappearing.

## How to use it

1. **Paste nested JSON** - Enter a valid JSON object or array in the left editor, or load the example.
2. **Choose the path style** - Select a separator, array index notation and output indentation to match the system that will use the keys.
3. **Review the flat result** - The output updates live, while the status line reports how many leaf paths were found and the deepest level visited.
4. **Copy the output** - Copy the flattened JSON and paste it into your mapping, spreadsheet, configuration or debugging workflow.

## Who it's for

- **API developers** turning nested responses into searchable path and value maps for debugging.
- **Data analysts** preparing hierarchical fields for spreadsheets, CSV headers or column mappings.
- **DevOps teams** comparing configuration values without scanning several levels of braces.
- **Form and app developers** creating stable field paths such as user.contact.email or items[0].sku.

## Expert note

A separator can already exist inside an original key: both a literal key named a.b and the nested path a then b flatten to a.b. This tool detects that collision instead of overwriting a value. Switch to slash or underscore, or rename the ambiguous key, before using the flat map as a reversible identifier.

## Frequently asked questions

### Is this JSON flatten tool free?

Yes. You can flatten JSON for free without an account, download or usage limit. The conversion uses your browser's built-in JSON parser and plain JavaScript.

### Is my JSON uploaded anywhere?

No. Parsing and flattening happen locally in your browser. The JSON you paste is not sent to a conversion server, which makes the tool suitable for internal payloads and configuration data.

### How large can the JSON input be?

There is no fixed service limit because nothing is uploaded. The practical limit depends on your browser's available memory. Very large documents can make any browser editor slow, so process huge data files with a streaming command-line tool instead.

### How are JSON arrays flattened?

Each array item receives its numeric index. Bracket style produces paths such as roles[0], while segment style uses roles.0 with a dot separator. You can switch styles without changing any values.

### Does flattening JSON change value types?

No. Strings remain strings, numbers remain numbers, and booleans and null keep their original JSON types. The tool changes only the object shape and path keys. Empty nested objects and arrays are preserved as values.

### What happens when a key contains the separator?

A key containing the chosen separator can produce the same path as a nested key. When that creates a collision, the tool shows an error instead of silently replacing data. Pick another separator or rename the conflicting key.

### Can I flatten JSON offline?

Yes. After the page has loaded, the converter needs no server request for the work itself. It can continue flattening JSON while your device is offline.

## Related tools

- [JSON to CSV Converter](https://candoya.com/tools/json-to-csv/)
- [CSV to JSON Converter](https://candoya.com/tools/csv-to-json/)
- [JSON Formatter](https://candoya.com/tools/json-formatter/)
- [JSON Minifier](https://candoya.com/tools/json-minifier/)

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*Markdown edition of <https://candoya.com/tools/json-flatten/>, published for AI agents and other automated readers. Index of key pages: <https://candoya.com/llms.txt>.*