How to use
- Paste or type your JSON in the left box. It is checked as you type.
- Choose the indentation — 2 spaces, 4 spaces, tabs, or Minify for a single line.
- Tick Sort keys to order object keys alphabetically, which makes two documents easier to compare.
- If there is an error, the message shows the line and column; otherwise copy or download the result.
Options explained
- Indent
- 2 spaces is the most common style (npm, Prettier); 4 spaces matches Python's json.dumps(indent=4); Minify removes all whitespace for the smallest size.
- Sort keys
- Sorts object keys by their decoded value, at every level. Array order is never changed.
- Big numbers
- Numbers are kept as written. Many formatters parse JSON into JavaScript numbers, which silently turns 12345678901234567890 into 12345678901234567000.
Common JSON errors and how to fix them
| Message | Typical cause |
|---|---|
Unexpected character ' |
Single quotes instead of double quotes |
| Trailing comma | A comma after the last item: [1, 2,] |
Unexpected character / |
A // comment copied from JavaScript |
| Document ends too early | Missing } or ], often from a truncated copy |
| Control characters must be escaped | A real tab or line break inside a string — use \t or \n |
| Unexpected content after the end | Two JSON documents pasted together, or text after the closing bracket |
Example
Input:
{"id":9007199254740993,"name":"Ada","tags":["math","code"]}Formatted with 2 spaces — note the ID is unchanged:
{
"id": 9007199254740993,
"name": "Ada",
"tags": [
"math",
"code"
]
}Frequently asked questions
Why does it say "trailing comma is not allowed"?
Standard JSON (RFC 8259) forbids a comma after the last item of an object or array, even though JavaScript allows it. Remove the comma before the closing } or ].
Can I use single quotes or comments in JSON?
No. JSON strings must use double quotes, and comments are not part of the format. Files like tsconfig.json accept them because their tools use a relaxed parser (JSONC).
Is my JSON sent to a server?
No. Parsing and formatting happen in your browser, so API responses, tokens and configuration files stay on your device.
Why do my large IDs change in other tools?
JavaScript stores numbers as 64-bit floating point, which is only exact up to 9,007,199,254,740,991. This tool never converts numbers, so IDs beyond that stay intact.
How large a file can it handle?
Documents of several megabytes format instantly on a laptop. For files of hundreds of megabytes, a command-line tool such as jq is a better fit.
Privacy
This tool runs entirely in your browser. Your files and text are processed on your device and are never uploaded to our servers.