Online tools
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.
How to use it
- Paste JSON into the text box above, or drop a .json file.
- Click "Format" for two-space indentation, or "Minify" to strip whitespace.
- 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 › 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.
In this section
Free file converters from Duaer
Free Duaer tools for spreadsheets and data files: convert formats, merge, split, remove duplicates, fix encodings, and format JSON. Everything runs in your browser and no file is uploaded.
File conversionJSON to CSV converter (nested JSON flattened)
A free Duaer tool: paste or upload JSON, nested fields become columns, and you download CSV or Excel. It runs in your browser with no upload.
File conversionCSV to JSON converter (free, no upload)
A free Duaer tool that turns each CSV row into a JSON object keyed by the header row. Optional number and boolean detection, GBK support, copy or download.
SnippetsSplit an array into separate items in Duaer
Duaer nodes run once per item. Split an order line list or an API array into one item per entry with Split Out so the next nodes handle each one.