> For the complete documentation index, see [llms.txt](https://doc.duaer.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.duaer.com/tools/json-formatter.md).

# JSON formatter and validator online (shows error line and column)

A free Duaer tool: paste or upload JSON to format or minify it, and see the exact line and column when it is invalid. Runs in your browser with no upload.

Interactive converter (runs in the browser, no upload): https://doc.duaer.com/tools/json-formatter/

## How to use it

1. Paste JSON into the text box above, or drop a .json file.
2. Click "Format" for two-space indentation, or "Minify" to strip whitespace.
3. Click "Copy" or "Download .json".

## Common errors

- Single quotes: JSON strings and keys need double quotes.
- Trailing comma: `[1, 2,]` is invalid.
- Unquoted keys: write `{a: 1}` as `{"a": 1}`.
- Comments: JSON does not allow `//` or `/* */`.

## Work with JSON in Duaer

In Duaer, JSON from HTTP Request is already parsed, so there is nothing to format; read fields with `{{ $json.field }}`. To save a .json file, use [Convert to File](/integrations/builtin/core-nodes/duaer-nodes-base.converttofile.md) › Convert to JSON and turn on Options › Format for indentation.
## Questions

### How is the error position found?

The Duaer formatter scans the text against JSON grammar and stops at the first invalid character. Lines and columns start at 1.

### Can it handle large JSON?

Yes. Duaer sets no limit; the preview shows the first 20,000 characters, while copy and download use the full result.

## Related

- [Free file converters from Duaer](https://doc.duaer.com/tools.md)
- [JSON to CSV converter (nested JSON flattened)](https://doc.duaer.com/tools/json-to-csv.md)
- [CSV to JSON converter (free, no upload)](https://doc.duaer.com/tools/csv-to-json.md)
- [Split an array into separate items in Duaer](https://doc.duaer.com/snippets/split-array-into-items.md)