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JSON formatter and validator
Format, minify and validate JSON while preserving large numbers and duplicate keys; inspect errors and a tree view. Inputs stay in this browser; no URL fetching or automatic saving. Files must be UTF-8.
No account needed
How to use
- 1Paste JSON or import a UTF-8 file.
- 2Choose indentation and optional key sorting, then format, minify or validate.
- 3Review error locations, duplicate keys and the tree; copy or download the result.
Good to know
Numbers, escapes, key order and duplicate keys are preserved. Sorting is optional. Limits: 1 MB, depth 200 and 50,000 nodes.
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When to use this tool
Use this to inspect API responses or check that large IDs have not changed. A token-preserving parser formats numbers without rounding; tree view and JSON Pointer help locate a value.
Worked input and output example
The public example below is processed by the same calculation or conversion code as the tool. No personal input or draft is used.
Example input
{"id":900719925474099312345,"active":true}Example result
{
"id": 900719925474099312345,
"active": true
}How to read and check the result
The example keeps 900719925474099312345 exactly. “Valid” refers to JSON syntax, not API schema or business-rule validation. Duplicate keys are reported and retained.