JSON Formatter
Validate, beautify or minify JSON
JSON Formatter: Turn a Wall of Data into Readable JSON
API returned one endless line? Paste, beautify, and see errors with line numbers.
JSON from APIs usually arrives as an unreadable single-line blob, while hand-written JSON breaks the moment a comma goes missing. This tool solves both: it validates whatever you paste instantly, then either pretty-prints it with 2 or 4 space indentation or minifies it to a single line for production. If there's a syntax error, it reports the location down to 'line 12, column 8' — no more comma hunting in huge files. Validation and formatting run entirely in your browser: JSON containing API keys or customer data never reaches any server.
Features
Instant Validation
Validity and error location appear as you type.
Beautify
Readable output with 2 or 4 space indentation.
Minify
Single line without wasted bytes for production.
Data Stays Yours
Everything runs in the browser — nothing is uploaded.
JSON Guide
Common mistakes
- Trailing comma after the last item: {"a":1,}
- Single quotes — JSON requires double quotes
- Unquoted keys: {a:1} is invalid
- Comments — JSON doesn't support them
Which mode when?
- Beautify: debugging, review, documentation
- Minify: API responses, configs, bandwidth
- 2 spaces: the modern standard (npm, VS Code default)
- 4 spaces: readability in deeply nested structures
Frequently Asked Questions
Why is my JSON invalid?
Four usual suspects: a trailing comma, single quotes, unquoted key names, and comment lines. The tool reports the error's line and column — look there and you'll find it in seconds.
Is my data sent to a server?
No. Validation and formatting use your browser's own JSON engine on your device. JSON containing API keys or personal data is safe to paste.
Does beautifying change my data?
No — only whitespace and line breaks are added; values, order and structure are preserved exactly. Minifying is equally lossless, it just strips redundant whitespace.
Should I use 2 or 4 spaces?
The modern ecosystem defaults to 2 spaces (npm, VS Code, most style guides). 4 spaces makes deeply nested structures easier to scan — it's a matter of preference.
How large a file can I process?
Anything that fits in browser memory; multi-megabyte API responses process instantly. For very large files, speed depends on your device since processing is local.
Why doesn't JSON support comments?
By design: JSON is a data interchange format, not a config language. If you need comments, use JSONC or YAML, or add a "_comment" field to the data.