JSON Formatter

What is the JSON Formatter?

A JSON formatter parses JSON text and re-prints it with consistent indentation — or minifies it to a single line — while flagging syntax errors, so you can read, debug and validate API responses, config files and package manifests.

How the JSON Formatter works

It parses your input against the JSON grammar (RFC 8259), builds the in-memory structure, then serialises it back out with the indentation you choose. If parsing fails it reports where and why — a trailing comma, a single-quoted string, an unquoted key or a stray character. Everything runs locally in your browser; nothing is uploaded.

Worked example

Input: {"name":"Ada","langs":["py","js"],"active":true} Formatted (2-space indent): { "name": "Ada", "langs": ["py", "js"], "active": true }

Key terms

Object:

An unordered set of key/value pairs wrapped in { }.

Array:

An ordered list of values wrapped in [ ].

Minify:

Strip optional whitespace to shrink the payload.

Pretty-print:

Re-indent the text for human reading.

Common mistakes to avoid

• Trailing commas after the last item — allowed in JavaScript, invalid in JSON.
• Single quotes or unquoted keys — JSON requires double quotes on keys and string values.
• Comments — JSON has none; strip // and /* */ or use JSONC/JSON5 instead.
• NaN, Infinity or undefined — none are valid JSON values.
• Integers beyond 2^53 — they lose precision; transmit them as strings.

Detailed FAQ