JSON Flattener

What is JSON flattening?

Flattening JSON converts a nested structure into a flat map of path-to-value pairs. Instead of objects inside objects, you get a single level where each key spells out the full path to its value — nested object keys are joined with dots (a.b.c) and array items use bracket indexes (list[0]). Flattened JSON is much easier to scan, diff, search, turn into a spreadsheet, or feed into systems that expect flat key-value data.

How to flatten JSON online

Flattening JSON with ToolsSoup takes just a few seconds:

1. Paste your nested JSON into the input box on the left.
2. Click Flatten to collapse it into a single-level object.
3. Copy the flattened JSON with one click.

What notation does the flattener use?

Object properties are joined with a dot, so a value at b inside a becomes a.b. Array elements use square brackets with their index, so a list of two items becomes list[0] and list[1]. Empty objects and empty arrays are kept as-is at their path, and all values — strings, numbers, booleans, and null — are preserved exactly. This is the same notation a JSON unflattener reverses to rebuild the original structure.

Why use this JSON flattener?

• 100% free with no ads, sign-up, or usage limits.
• Runs entirely in your browser — your data is never uploaded to a server.
• Uses clear dot and bracket notation for nested keys.
• Preserves empty objects, empty arrays, and all value types.
• Works offline once the page has loaded.

Frequently asked questions