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JSON Formatter: Beautify, Validate & Minify JSON Online

JSON formatter and validator online: beautify, minify, and validate JSON with syntax highlighting, error messages, and tree view.

Updated 2026-08-16

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Features

  • Real-time JSON formatting as you type: paste and it formats instantly
  • Syntax highlighting with color-coded keys (purple), strings (green), numbers (blue), booleans (amber), and nulls (red)
  • Collapsible tree view for exploring nested JSON structures at any depth
  • Instant validation with precise error location: highlights the exact line number in red when JSON is invalid
  • Key sorting: alphabetize object keys for consistent output across environments
  • Custom indentation: choose 2 spaces, 4 spaces, or tab to match your project's style guide
  • Line numbers displayed by default for easy reference when debugging or comparing diffs
  • One-click minify to compress JSON for production APIs or reduce payload size
  • Drag-and-drop files or click to browse: supports any .json file
  • One-click copy to clipboard for easy sharing and pasting into other applications
  • Download formatted output as .json file or copy to clipboard in one click

How to Use

  1. 1Paste JSON into the left editor; it formats automatically as you type. Or drag a .json file onto the page.
  2. 2Switch between Formatted view (pretty-printed), Tree view (collapsible nodes), and Minified (compressed) using the tabs.
  3. 3Click the indent buttons (2 / 4 / Tab) to change spacing. Toggle Sort Keys to alphabetize object keys.
  4. 4When validation fails, the error line number turns red in the left panel; click it to jump to the problem.
  5. 5Click Copy or Download on the right toolbar to save your formatted JSON.
  6. 6In Tree view, click the triangle arrows to expand or collapse nested objects and arrays for easier exploration.
  7. 7Use the Upload button to open a .json file from your device instead of pasting manually.
  8. 8Toggle the Minified tab to compress JSON for production, great for reducing API payload size.
  9. 9Use the Copy button to grab the output in any view mode: formatted, tree, or minified.

Frequently Asked Questions

What is JSON formatting?

JSON formatting (also called beautifying or pretty-printing) adds proper indentation and line breaks to compact JSON data. This makes it readable, easier to debug, and simpler to edit. Most APIs return minified JSON to save bandwidth; this tool reverses that so you can actually read it.

How do I format JSON in Notepad++ or VS Code?

VS Code has it built in: open the file and press Shift+Alt+F (or right-click > Format Document). Notepad++ needs a plugin: install JSON Viewer from Plugins Admin, then Plugins > JSON Viewer > Format JSON. This web tool produces the same result without installing anything.

Is there a Chrome extension for formatting JSON?

Yes, extensions like JSON Formatter pretty-print JSON URLs in the browser and are handy for API debugging, but they only run on pages you visit and require extension permissions. This web tool formats pasted JSON or uploaded files from any source, works offline, and needs neither installation nor permissions.

What does the error line highlight mean?

When you paste invalid JSON (missing comma, trailing comma, unquoted key, etc.), the validator detects the exact position of the error. The corresponding line number in the left panel turns red, and the error message below shows the line number and column position so you can fix it quickly.

What's the difference between Format and Minify?

Format (or beautify) expands JSON with indentation and newlines for readability; use this for debugging, editing, or documentation. Minify removes all whitespace to produce the smallest possible output; use this for API responses, reducing file size, or embedding JSON in HTML attributes where space matters.

Does it support comments or trailing commas?

No. Strict JSON (RFC 8259) does not allow comments (// or /* */) or trailing commas. If your input contains these, the validator will report an error. For JSONC (JSON with comments), consider stripping comments before pasting, or use a JSONC-specific parser.

How do I copy the formatted JSON?

Click the Copy button on the right toolbar to copy the entire formatted output to your clipboard. You can also click Download to save it as a .json file.

Why does formatting a very large JSON file slow down?

Browser rendering limits become noticeable above 50 MB; files within 5-10 MB usually format instantly on modern browsers. The practical limit also depends on your device's available memory. For extremely large files, use a command-line tool like `jq` or Python's `json.tool` module instead.

Can I use this on mobile?

Yes. The layout automatically adapts to smaller screens; input and output panels stack vertically on mobile devices. All features including formatting, tree view, copy, and download work on touch screens. Drag-and-drop upload also works on mobile browsers that support the File API.

How do I copy just a portion of a large JSON?

In Tree view, right-click (or long-press on mobile) on any node to copy only that sub-tree. In Formatted view, select the exact text you want with your cursor, then copy normally. The toolbar Copy button always copies the full output. For large files, consider using Tree view to navigate to the relevant section first.

Why does my formatted JSON have keys in a different order?

Because the Sort Keys option is on: it alphabetizes every object key in the JSON output; turn it off to keep keys exactly as written. Sorting is useful when: (1) comparing two JSON files side by side: sorted keys make diffs cleaner, (2) generating consistent output for version control to prevent false diffs, (3) when your team's coding standards require alphabetical key ordering. Note: JSON arrays maintain their original order.

Why is my JSON rejected even though it looks perfectly valid?

The usual suspects are invisible characters: a BOM (byte order mark), zero-width spaces, or non-breaking spaces that sneak in when you copy text from Word, Excel, or some web pages. Strict parsers reject them. If a json formatter online says 'invalid' but the JSON looks fine, paste it into a hex-aware editor to spot the invisible bytes, or retype the characters around the reported position.

Why does my JSON formatter and validator reject NaN or Infinity?

Strict JSON (RFC 8259) has no NaN or Infinity: only numbers, strings, booleans, null, arrays, and objects. JavaScript's JSON.parse rejects them too, which is why APIs that return NaN must stringify it or replace it with null first. This tool follows the same strict rule by design, so the rejection is a spec compliance issue, not a tool bug.

Why can't JSON validation check whether a date is a real date?

JSON has no date type; a date is just a string, and a validator can only check string syntax, not whether '2026-02-30' is a real calendar date. If you need real date validation, validate the field in your application code after parsing, or use a JSON Schema that applies a pattern to the field.