JSON Formatter

How it works in FileLume

• FileLume calls JSON.parse on the pasted or selected JSON and JSON.stringify with the selected indent size.
• Invalid JSON is rejected instead of being silently rewritten.

Best for

• Making compact API responses easier to read.
• Checking whether a JSON document is syntactically valid.
• Creating a consistently indented copy before review or version control.

Format and quality guidance

• The input must be valid JSON, including double-quoted property names and strings.
• Indentation changes presentation only; it does not change keys, values, or data types.

Trade-offs to expect

• Formatting increases file size because whitespace is added.
• JSON.stringify normalizes whitespace and does not preserve comments because comments are not valid JSON.

Limitations

• Very large JSON documents can make the browser tab slow or consume substantial memory.
• This tool validates syntax but does not validate a business schema or API contract.

Common errors and fixes

The JSON cannot be parsed.

Check for trailing commas, single quotes, comments, missing braces, or unescaped characters.

Comments disappeared.

Use a JSON-compatible format without comments; standard JSON does not preserve them.

The output is much larger.

Choose a smaller indent or minify the JSON for transport.

JSON Formatter FAQ