Free JSON Formatter
Beautify, minify, validate, and repair JSON — with a collapsible tree view. Everything runs in your browser; your data never leaves your device.
What is a JSON formatter?
A JSON formatter is a tool that takes raw JSON and re-indents it into a clean, readable structure — or compresses it back to a single line. It validates the JSON as it goes, so a missing comma or bracket is caught immediately, and it can show the data as a collapsible tree.
This formatter runs entirely in your browser using the built-in JSON parser. Your data is never uploaded, stored, or sent anywhere — it stays on your device.
How to format JSON
Paste or upload JSON
Paste JSON into the box, or use Upload to load a .json file.
Format, repair, or explore
Press Format to beautify, Repair to fix broken JSON, or Tree view to browse the structure.
Copy or download
Copy the result to your clipboard, or download it as a file.
What this tool offers
Beautify & minify
Re-indent messy JSON, or compress it to a single line.
Collapsible tree view
Browse nested JSON as an expandable tree.
JSON repair
Fix trailing commas, single quotes, unquoted keys, and comments automatically.
Live validation
Instant valid/invalid status with the exact error line.
Sort keys, upload & download
Sort object keys alphabetically; load and save files.
100% in your browser
Your JSON never leaves your device — fully private.
Before and after
The same JSON, minified and formatted.
{"name":"Knowster","plan":"pro","tags":["ai","chat"],"active":true}
{
"name": "Knowster",
"plan": "pro",
"tags": [
"ai",
"chat"
],
"active": true
}
Why format JSON?
Raw JSON from an API or a log is often a single unbroken line — technically valid, but almost impossible to read. Formatting it adds indentation and line breaks so the structure becomes visible at a glance: which keys belong to which object, where an array starts and ends. A tree view goes further, letting you collapse the parts you do not care about.
Formatting also surfaces mistakes. A trailing comma, an unquoted key, or a missing bracket stops the JSON from parsing — and this tool points to the exact line, or repairs the common cases for you. Minifying does the reverse: it strips every optional space so the payload is as small as possible for production.
Working with JSON: best practices
Do
- Format JSON before reading or debugging it.
- Minify JSON for production payloads and storage.
- Use double quotes around every key and string.
- Validate JSON before sending it to an API.
Don't
- Leave a trailing comma after the last item.
- Use single quotes — JSON requires double quotes.
- Add comments — standard JSON does not allow them.
- Paste sensitive data into tools you do not trust.
Frequently asked questions
Is this JSON formatter safe and private?
Yes. The JSON is parsed entirely in your browser with the built-in JSON engine. Nothing is uploaded, stored, or sent to a server — your data stays on your own device. Many popular formatters process data on their servers; this one never does.
What is the difference between format and minify?
Format adds indentation and line breaks to make JSON readable. Minify removes every optional space and newline to make the file as small as possible. Both produce the same valid JSON — only the whitespace differs.
Can it fix invalid JSON?
Yes — the Repair button attempts the common fixes: it removes comments and trailing commas, converts single quotes to double quotes, and adds quotes around unquoted keys. It is best-effort, so deeply broken JSON may still need a manual edit.
What does tree view do?
Tree view shows the JSON as a collapsible hierarchy. You can fold objects and arrays you do not need, which makes large, deeply nested JSON far easier to navigate than a flat text block.
Why won't my JSON parse?
The most common causes are a trailing comma after the last item, single quotes instead of double quotes, an unquoted key, or a missing bracket or brace. The tool shows the error and the line number — or try Repair to fix it automatically.
Is there a size limit?
There is no server limit because nothing is uploaded. Very large JSON files are limited only by your browser's memory and may format slowly on an older device.
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