Format and Validate JSON

What is JSON Formatter?

Format, validate, and minify JSON in one screen. Live syntax-error reporting tells you the exact line and column where parsing broke; a toggle lets you sort object keys for deterministic output useful in diffs and snapshots. Handles deeply nested structures, accurately round-trips numbers within JavaScript's safe-integer range, and shows byte counts before and after.

How do I use JSON Formatter?

1. Paste JSON into the input panel.
2. Choose Pretty or Minify mode, and set indent size.
3. If valid, the output panel shows the formatted JSON with syntax highlighting.
4. Copy or download the result.

JSON Formatter by the numbers

Parser

Native JSON.parse

Indent options

2, 4, or tab

Max comfortable size

~50 MB

Error reporting

Line + column of first error

Key-sort

Optional, alphabetic, recursive

Common use cases for JSON Formatter

• Pretty-printing an API response captured from a browser Network tab.
• Diffing two JSON configs after alphabetising keys.
• Preparing a README example from a minified payload.
• Spotting a trailing comma or missing quote in a broken manifest.
• Normalising fixtures before committing them to a test suite.

Common pitfalls and how to avoid them

• Parser complains about trailing commas — Strict JSON bans trailing commas. Remove them or paste into a JSON5-capable tool first.
• Keys come out in an unexpected order — Toggle off "Sort keys" if you want to preserve insertion order. Toggle it on for deterministic diffs.
• Large file freezes the tab — JSON.parse blocks the main thread on huge inputs (tens of MB). Split the file or use a streaming parser outside the browser.

When should I use JSON Formatter?

Beautifier is the right tool for formatting and validation. For aggressive minification only (one-line output), use JSON Minifier. To generate TypeScript interfaces from a JSON sample, use JSON to TS.