How to Format, Validate and Debug JSON Like a Pro

JSON is everywhere: configuration files, REST APIs, logs and browser storage. When it is minified or broken, it is painful to read. Formatting and validation turn that pain into a quick fix.

What JSON formatting does

Formatting, or pretty-printing, takes a valid JSON string and adds consistent indentation and line breaks so its structure is easy to scan. Validation checks whether the text is actually valid JSON, and if it is not, reports the exact location of the error.

Why it matters

• Minified JSON is compact but unreadable for humans.
• A missing comma or quote breaks parsers with an often-confusing error.
• Pretty output makes nested objects and arrays obvious.

Formatting in common languages

JavaScript:

const value = JSON.parse(input)
const pretty = JSON.stringify(value, null, 2)

Python:

import json
parsed = json.loads(input_text)
pretty = json.dumps(parsed, indent=2)

PHP:

$value = json_decode($input, true);
echo json_encode($value, JSON_PRETTY_PRINT);

Common JSON mistakes

• Trailing commas, which JavaScript allows but strict JSON does not.
• Using single quotes instead of double quotes.
• Unescaped quotes inside string values.
• Comments, which are not part of the JSON specification.

Frequently asked questions

• Is my JSON data uploaded anywhere? No. A good formatter runs entirely in your browser.
• Why does my JSON parse but look broken? It is probably valid but minified; formatting fixes readability.
• How do I find an error fast? Use a validator that reports the exact line and column.

Need a clean, private way to format and validate JSON? Try the free JSON Formatter & Validator — everything stays in your browser.