JSON Formatter Online — Beautify, Validate & Diff

Format, minify, validate, sort, repair and explore JSON — all in your browser, nothing uploaded.

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Free JSON Formatter, Validator & Diff Tool — No Upload

This free online JSON formatter and JSON beautifier runs entirely in your browser using JavaScript's native JSON.parse() and JSON.stringify() APIs. Nothing is uploaded to a server — your JSON data never leaves your device. Paste any JSON and get instant formatting, validation, and error messages with the exact character position of any syntax mistake.

Beyond basic formatting, this tool covers the full JSON editing workflow: minify for production, sort keys for consistent output, auto-repair broken JSON, explore nested structures in an interactive tree view, and diff two JSON objects side-by-side. Formatted output can be copied to clipboard or downloaded as a .json file.

Everything This JSON Tool Can Do

  • Format / Beautify — Indent JSON with 2 spaces, 4 spaces, or tabs. Instantly readable output from any minified blob.
  • Minify — Strip all whitespace for compact output, ideal for APIs and config files where file size matters.
  • Validate — Know immediately if your JSON is valid, with a precise error message pointing to the exact failure.
  • Sort Keys — Recursively sort all object keys alphabetically for consistent, diffable, version-control-friendly output.
  • Repair — Automatically fix trailing commas, single-quoted strings, and unquoted keys — the most common mistakes in hand-written JSON.
  • Tree View — Explore deeply nested JSON as a collapsible interactive tree. Collapse nodes to focus on what matters.
  • Diff — Paste two JSON blobs side-by-side and see exactly which lines changed — useful for comparing API responses or config versions.
  • Download — Save formatted output as a .json file with one click.

Who Uses a JSON Formatter?

Backend developers paste API responses to debug unexpected data shapes. Frontend developers format config files before committing to version control. QA engineers diff two JSON payloads to verify an API change didn't break the response structure. DevOps engineers validate JSON configs before deploying. Students learning REST APIs use the tree view to understand nested data without reading raw text.

The Repair feature specifically helps anyone working with hand-written JSON or JavaScript object literals — single quotes, trailing commas, and unquoted keys are all fixed automatically, saving time over manual editing. Need to compare full PDF documents instead? Try the PDF Diff tool. Working with plain text or writing content? The Word Counter & Text Analyzer runs the same way — instant, private, no upload.

Frequently Asked Questions

What is a JSON formatter?

A JSON formatter (also called a JSON beautifier or JSON pretty printer) takes compact or poorly-indented JSON and adds consistent whitespace and newlines to make it human-readable. Developers use formatters when debugging API responses, reading config files, or reviewing data.

What does minify do?

Minifying removes all unnecessary whitespace and newlines from JSON, making it as compact as possible. This reduces file size and is used in production APIs and bundled configs where bandwidth or storage matters.

Is my JSON data safe?

Yes. All operations run entirely in your browser using JavaScript. Nothing is sent to any server — not your JSON content, not your IP, nothing. You can even use this tool offline once the page is loaded.

Why does it say "Invalid JSON"?

JSON has strict rules: keys and string values must use double quotes, trailing commas are not allowed, and all brackets must be properly closed. The error message shows the exact character position of the failure. Use the Repair button to auto-fix the most common mistakes.

What does the Repair feature do?

Repair attempts to fix the most common JSON authoring mistakes: trailing commas before closing brackets, single-quoted strings instead of double-quoted, and unquoted object keys. It's useful when working with hand-written or JavaScript-object-style data.

How does the JSON diff work?

The Diff tab parses both JSON inputs, formats them with consistent indentation, then compares them line-by-line. Differing lines are highlighted so you can quickly spot what changed between two versions of a JSON document.

How do I format JSON online for free?

Paste your JSON into the input box and click Format / Beautify. The result appears instantly with proper indentation. Choose 2 spaces, 4 spaces, or tabs using the indent selector. Free, no signup, no upload.