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Paste · Format · Validate · Minify

Indent and validate JSON. Runs in your browser.

Indent
Result184 B
{
  "name": "util-platform",
  "heroTool": "json-format",
  "tools": [
    "json-format",
    "image-compress",
    "color-palette",
    "qr-code",
    "unit-convert",
    "diff"
  ]
}
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When to use it

When one-line JSON is unreadable, or when you want to check that a file is valid. Paste it in and it's indented cleanly — any mistake is flagged with the exact line and column.

How it works

Paste on the left and the right updates as you type. Pick an indent width at the top, or "Minify" to collapse to a single line. Turn on "Sort keys" for a consistent order.

Common mistakes

  • Stray commas — missing one, or leaving one trailing on the last item. The most common error.
  • Unbalanced brackets — { or [ opened but not closed.
  • Single quotes — JSON only accepts double quotes. 'hello' → "hello".
  • Literal newline in a string — use \n, not an actual Enter keystroke.
  • Two top-level objects — wrap them in an array, or confirm you meant JSON Lines.

API responses never leave this page

Auth tokens, user IDs, payment fields embedded in JSON are safe. Parsing uses native `JSON.parse` — zero external libraries. The formatted result stays inside the page.

Frequently asked questions

Why won't my JSON parse?
The most common causes: (1) trailing commas — a comma after the last item violates the JSON spec, (2) single quotes — JSON only allows double-quoted strings, (3) unmatched brackets. When parsing fails, the result pane shows the exact line and column to check.
Is the JSON I paste sent to a server?
No. All processing happens in this page's JavaScript with zero outbound network requests. You can verify this in your browser's DevTools Network tab.
What's the difference between Minify and Beautify?
Beautify (2/4/Tab indent) adds whitespace and line breaks for readability. Minify removes all whitespace into one line — useful for reducing transfer size. The data semantics are identical.
Can I sort JSON keys alphabetically?
Yes. Toggle "Sort keys alphabetically" in the options bar. Every nested object gets sorted lexicographically. The toggle has no visible effect in Minify mode (key order isn't shown).
What's the maximum JSON size I can format?
Recommended under 5MB. Beyond that, browser memory and responsiveness become limiting. Files over 10MB usually need a streaming parser, which this tool does not implement.