How JSON Formatter Works
The formatter parses your input with a standard JSON parser, then rewrites it with consistent indentation and line breaks. If the JSON is invalid, the parser's own error is translated into a line and column number so you can find the problem quickly instead of scanning the whole file.
How to Use This Tool
- Paste or type your JSON into the input box on the left.
- Choose an indent size — 2 spaces, 4 spaces, or a tab.
- Select Format & Validate.
- Valid JSON appears neatly indented on the right; invalid JSON shows exactly where the problem is.
Example
Input {"id":1,"tags":["a","b"],"active":true} formatted with a 2-space indent becomes:
{
"id": 1,
"tags": [
"a",
"b"
],
"active": true
}Helpful Tips
- A trailing comma after the last item in an object or array is the most common reason JSON fails to parse — the formatter's error message will point at it.
- Use the 4-space or tab indent if you're pasting the result into code that follows a different style guide.
- This also works as a JSON validator — if the success message appears, your JSON is syntactically valid.
Frequently Asked Questions
Does this tool validate JSON as well as format it?
Yes — formatting requires parsing the JSON first, so if it formats successfully, it's valid JSON. Invalid input shows a specific error instead.
Why does it show a line and column number for errors?
The browser's JSON parser reports the character position where parsing failed; the tool converts that into a line and column so you can locate it in your editor.
Can I format very large JSON files?
Yes, though extremely large files (tens of megabytes) may be slow since parsing happens in your browser rather than on a server.
Is my JSON uploaded anywhere?
No, parsing and formatting both happen locally in your browser.
This tool runs entirely in your browser. Your input is not uploaded to any server.