JSON Formatter & Beautifier
This JSON formatter turns minified or messy JSON into a clean, indented document with syntax highlighting, line numbers, and collapsible sections for nested objects and arrays. It detects syntax errors and marks the exact line where parsing fails, so malformed JSON is easy to locate and fix. Formatting runs entirely in your browser — no upload, no signup, no server round trip.
How to format JSON online
- Paste your minified or messy JSON into the input on the left.
- The formatted, indented result appears on the right — with line numbers and code folding.
- Click Copy or Download to save the output.
Common use cases
- Reading an API response you copied out of a log line.
- Preparing a JSON payload for documentation.
- Spotting missing brackets or trailing commas.
Frequently asked questions
How do I format JSON online?
Paste your JSON into the editor and it is formatted automatically with two-space indentation, line numbers, and code folding — no button click required. Use the copy or download button to grab the formatted result.
Is my JSON data uploaded to a server?
No. The formatter parses and re-indents your JSON entirely in your browser, so the content never leaves your device or gets logged anywhere.
Why does my JSON show as invalid?
The most common causes are trailing commas, single-quoted strings, unquoted object keys, or unescaped control characters inside strings — strict JSON forbids all of these. The editor highlights the exact line and column of the first error so you can jump straight to the problem.
Can I collapse and expand nested objects and arrays?
Yes. Every object and array has a fold control in the gutter, so you can collapse deeply nested sections and focus on the part of the document you are editing.
What is the difference between formatting and validating JSON?
Formatting reindents and highlights JSON that is already parseable, while validation checks whether the JSON is syntactically correct in the first place. This tool does both — it will not format text it cannot parse, and it reports the parse error instead.
Related tools
JSON Viewer
This JSON viewer renders any document as a collapsible tree so you can explore large payloads without scrolling.
JSON Minifier
This JSON minifier strips whitespace and line breaks to shrink payload size for APIs and config files.
JSON Validator
This JSON validator checks syntax instantly and pinpoints the exact line and column of any error.