JSON Flattener Convert
Flatten deeply nested JSON into dot-notation keys, or expand it back.
JSON Flattener is a free online tool that flatten deeply nested JSON into dot-notation keys, or expand it back. It runs entirely in your web browser using plain JavaScript, so files are processed on your own device and never uploaded to a server. There is no sign-up, no file size limit imposed by the site, no watermark and no paid tier.
- Price
- Free — no account, no quota, no watermark
- Category
- Convert
- Where it runs
- In your browser, on your device
- Files uploaded
- None
- Technology
- plain JavaScript
- Settings
- 2
- Works offline
- Yes, after the first visit
About JSON Flattener
Nested structure is collapsed into single-level keys joined by dots — `{"user":{"address":{"city":"Leeds"}}}` becomes `{"user.address.city":"Leeds"}`. This is what you need before loading JSON into a spreadsheet, a CSV, a feature-flag system or anything else that expects flat key-value pairs. Array indices become numeric path segments.
How to use it
- Paste the text you want to run through json flattener.
- Set direction and separator.
The 2 settings
| Setting | What it does | Default |
|---|---|---|
| Direction | Choose from 2: Flatten, Expand back. | Flatten |
| Separator | Free text. | . |
Under the hood
| Runs on | plain JavaScript — runs the whole thing |
| Controls | Direction, Separator |
Questions
Can it be unflattened?
Usually, but not always — a literal dot inside an original key is indistinguishable from a path separator once flattened. Choose a separator that does not appear in your keys if you need to reverse it.
How are arrays handled?
By index: `items.0.name`, `items.1.name`. That preserves order and position, which bracket notation would too — the dot form is simply more common in config systems.