JSON Formatter & Validator

What a JSON formatter actually does

A JSON formatter takes a string of JSON and rewrites it with consistent indentation, line breaks, and key spacing so a human can read it. Minified JSON that arrives from an API is usually a single line with no whitespace, which saves bandwidth but is painful to scan. Formatting (also called beautifying or pretty-printing) does not change the data, only its layout. A good formatter also validates: if the input is not valid JSON it reports the position of the error instead of silently producing garbage.

When you reach for it

The common cases are reading a response copied from browser dev tools, inspecting a config file that was saved minified, diffing two payloads to see what changed, or cleaning up JSON before pasting it into a bug report. Formatting also surfaces structural mistakes fast: a missing comma, a trailing comma (which standard JSON forbids), or single quotes used instead of double quotes.

Example

Minified input:

{"id":42,"tags":["a","b"],"active":true}

Formatted output with two-space indentation:

{
  "id": 42,
  "tags": ["a", "b"],
  "active": true
}

Common pitfalls

JSON is stricter than JavaScript object literals. Keys must be double-quoted strings, strings cannot use single quotes, comments are not allowed, and NaN or Infinity are not valid values. Numbers do not keep leading zeros, and very large integers can lose precision once parsed into a floating point number.

FAQ

Does formatting change my numbers? The visible digits stay the same, but if you re-serialize after parsing, an integer like 9007199254740993 may come back rounded because it exceeds the safe integer range for doubles.

Why does my input with // comments fail? Those are JSONC or JSON5 features, not standard JSON. Strip comments first, or use a parser that explicitly supports them.

Can it sort keys? Formatting preserves key order by default. Sorting is a separate step and will reorder your object, which matters if order carries meaning in your system.