{} JSON Formatter

What is JSON Formatter?

Paste a messy, minified, or string-escaped blob of JSON on the left and get a properly-indented, syntax-highlighted, validated version on the right — instantly, no button press. The formatter parses your input with a strict JSON parser, so any trailing comma, single quote, or unescaped character fails fast with a line and column number pointing at the problem. Works on anything from a tiny API response to a multi-megabyte configuration file. The entire parse and render runs in your browser, so you can paste API keys, customer records, or other sensitive payloads without them ever leaving your machine.

How to Use

1. Paste your JSON into the left panel
2. See formatted, syntax-highlighted output instantly on the right
3. Errors are highlighted in red with line numbers
4. Click "Copy" to copy the formatted result or "Minify" to compress it

Common JSON mistakes the formatter will catch

Most JSON parse errors come from a handful of violations of the spec. The formatter flags each of them with a line and column pointer. The usual suspects:

• Trailing commas — valid in JavaScript objects and arrays, not valid in JSON. {"a": 1, "b": 2,} is a syntax error.
• Single quotes — JSON mandates double quotes on both keys and string values. {'name': 'Alex'} fails; {"name": "Alex"} works.
• Unquoted keys — {name: "Alex"} is valid JavaScript but not JSON. Keys must always be quoted strings.
• Escaped characters — literal newlines, tabs, or unescaped backslashes inside string values break the parse. Use the escape sequences for newline, tab, and backslash instead.
• Non-finite numbers — NaN, Infinity, and -Infinity are not valid JSON values; they must be expressed as strings or omitted.
• Comments — JSON does not allow // or /* */ comments. If you need commented config, look at JSON5 or JSONC instead.

Pretty vs. minified: when to use each

"Pretty" JSON with 2- or 4-space indentation is for humans — reading, debugging, and diffing in git. It's what you want in config files, API documentation, and test fixtures. The downside: whitespace adds bytes. A deeply nested object can be 30–50 % larger pretty-printed than minified.

"Minified" JSON strips all non-essential whitespace — no line breaks, no indentation, no spaces after commas or colons. It's for wire transfer: HTTP request/response bodies, localStorage entries, cached payloads, anything where bytes-per-request matters. Most web servers also gzip-compress JSON in transit, which eats most of the pretty-vs-minified difference, but minification still saves on the parsing step and on storage at rest.

General rule: pretty-print in source control and documentation, minify over the wire. The formatter supports both — paste, click Minify or just copy the indented output.

What this tool will not do (and what will)

This is a formatter and validator, not a query tool or transformer. It won't:

• Extract a nested value — for that, use jq on the command line or JSONPath in a code editor.
• Compare two JSON objects — use a JSON diff tool. We may add one later.
• Convert to YAML / TOML / XML — separate converter tools handle that.
• Fix broken JSON — the parser is strict. If your input is malformed, you'll see the error location but the tool won't auto-repair. "JSON repair" algorithms exist but they guess at your intent and often guess wrong.

What it will do well: take any valid JSON (object, array, primitive — even 42 alone is valid JSON), format it for readability, highlight syntax, and let you copy or minify the result with one click. Everything runs locally, so pasting credentials or customer data is safe.

Frequently Asked Questions

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