Data formatters
JSON Formatter and Validator
Format, validate, and minify JSON locally with clear error messages.
{
"hello": "world"
}How to use this tool
Paste JSON into the editor or drop a local JSON file.
The formatter parses the input first, so invalid JSON shows a real parse error instead of silently changing your data.
Use the formatted output for review, debugging, documentation, or before converting JSON to YAML or CSV.
Common JSON errors this helps catch
JSON requires double quotes around object keys and string values. Single quotes and unquoted keys are valid in JavaScript objects, but not in JSON.
Trailing commas after the last object property or array item are not allowed in JSON.
Escaped characters matter. If a string contains quotes, backslashes, or line breaks, they must be represented correctly.
Privacy and limitations
Formatting runs in your browser. Lumio does not store the JSON input or formatted output for analytics.
Very large JSON files can still be limited by browser memory. For production logs or multi-megabyte exports, split the file before pasting it into any browser tool.
Examples
Compact object to readable JSON
Input{"name":"Lumio","private":true,"tools":["JSON","YAML"]}Output{
"name": "Lumio",
"private": true,
"tools": [
"JSON",
"YAML"
]
}Invalid trailing comma
The parser reports an error because JSON does not allow a trailing comma after the last property.
Input{"name":"Lumio",}FAQ
Why does valid JavaScript fail as JSON?
JSON is stricter than JavaScript object syntax. JSON does not allow comments, trailing commas, single-quoted strings, or unquoted property names.
Does formatting change the data?
The formatter parses the JSON and serializes it with indentation. It preserves data values, but object key order follows the parsed object order in the browser.
Can I validate JSON Schema here?
Use the JSON Schema Validator tool when you need to check required fields, types, arrays, enum values, and other schema rules.
Is my JSON uploaded to Lumio?
No. This formatter runs locally in your browser and tool inputs are not stored for analytics.