03 / DEVELOPER
JSON Formatter
Pretty-print, minify and validate JSON in your browser. Detects syntax errors with line and column hints. Nothing leaves your device.
How to use
- 1Paste your JSON into the Input panel on the left.
- 2The Output panel renders the formatted result as an interactive tree with line numbers in a left gutter. Indent defaults to 4 spaces; switch to 2 with the indent control.
- 3Click the toggle on any object or array to collapse it, or use the panel's Collapse all / Expand all buttons.
- 4Click Minify to collapse the JSON onto a single line, or Format to switch back to the tree view.
- 5If your input is invalid, the error bar shows the failure with the offending line and column.
Frequently asked questions
Is my JSON sent to a server?
No. Parsing and formatting use your browser's native JSON.parse and JSON.stringify. Nothing leaves your device.
How do I read the error message?
We pass through the browser's parser error and append the line and column inferred from the byte position, e.g. "Unexpected token } at position 28 (line 4, col 12)".
Can it handle very large JSON?
Inputs up to a few megabytes work fine. Beyond that you may notice a delay; the format runs synchronously, so the page is briefly blocked while parsing.
Are JSON5, JSONC or trailing commas supported?
Yes — switch the parser toggle to Lenient. The lenient mode runs json5 and accepts comments, trailing commas, single-quoted strings, hex numbers, and the rest of the JSON5 spec. Strict mode (default) keeps to the JSON RFC.