JSON Formatter & Validator
Format, validate, and minify JSON instantly in your browser.
JSON has become the default data interchange format for APIs, configuration files, and logs, which means every developer eventually ends up staring at a wall of unformatted JSON pasted from a server response, a log line, or a Slack message and needing to actually read it. A JSON formatter takes that flat, whitespace-free string and re-indents it into a readable tree structure, while simultaneously validating that the JSON is syntactically correct — a single missing comma or unescaped quote anywhere in a large payload can otherwise take minutes to spot by eye.
This tool runs entirely in your browser using the same JSON.parse and JSON.stringify functions built into JavaScript, so there's no server round-trip, no upload size limit beyond what your browser can hold in memory, and no risk of sensitive data (API keys, tokens, user records) leaving your machine. Paste your JSON, click Format, and get a clean, indented result with clickable error messages if something's wrong. The minify option does the reverse — stripping all non-essential whitespace to produce the smallest possible payload, which is useful when you need to paste JSON into a size-constrained field or embed it in a single-line config value.
Both operations preserve the exact data in your JSON — no keys are reordered, no values are coerced, and no precision is lost on numbers within the limits of what JavaScript's number type can represent. If your JSON contains very large integers (larger than 2^53), be aware that JavaScript's JSON parser will round them, which is a limitation of the language itself rather than this tool.
How to use JSON Formatter & Validator
- 1
Paste your JSON
Paste or type your raw JSON into the input box on the left.
- 2
Choose an indent size
Pick 2, 4, or 8 spaces depending on your project's style guide.
- 3
Click Format & Validate
The tool parses your JSON and either shows a formatted result or a clear error message with what went wrong.
- 4
Copy the result
Use the Copy result button to grab the formatted (or minified) output onto your clipboard.
Features
- Runs entirely client-side — your JSON never leaves your browser
- Instant syntax validation with readable error messages
- Adjustable indentation (2, 4, or 8 spaces)
- One-click minify for producing compact JSON payloads
- No file size limit imposed by a server upload
Frequently asked questions
Common mistakes to avoid
- Using single quotes instead of double quotes around strings and keys — this is valid in JavaScript object literals but invalid JSON.
- Leaving a trailing comma after the last item in an array or object.
- Forgetting to escape special characters like newlines or quotes inside string values.
- Assuming very large integers will keep full precision — JavaScript's number type rounds integers above 2^53.
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