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Free JSON Formatter & Validator Tool Online

Beautify, validate, and minify JSON with instant syntax error detection and line numbers. Fast, browser-based, and privacy-friendly.

IN: JSON text  ·  OUT: Formatted JSON  ·  RUNS: 100% in your browser

indent
// formatted output appears here

Frequently asked questions

Is my JSON data uploaded anywhere?+

No. Formatting and validation run entirely in your browser using JavaScript. Your JSON never leaves your device.

Can this tool fix invalid JSON?+

It highlights the exact position where parsing fails so you can fix syntax errors like trailing commas, missing quotes, or unescaped characters, but it does not auto-repair JSON for you.

What indentation does the formatter use?+

You can choose between 2 spaces, 4 spaces, or tab indentation using the control above the output panel, matching whichever style your project or team prefers.

Is there a file size limit?+

The tool can comfortably handle JSON documents of several megabytes since processing happens locally, without a server round trip or upload wait.

What's the difference between formatting and validating?+

Formatting reorganizes valid JSON into a readable, indented structure. Validation is a side effect of that process — if the JSON can't be parsed, the tool shows an error instead of output, effectively confirming whether it's valid.

Does this tool support JSON5 or JSONC (comments)?+

No, it follows the strict JSON specification (RFC 8259), which doesn't allow comments or trailing commas. If your input includes those, remove them first or the parser will report an error.

Can I minify JSON instead of beautifying it?+

This tool focuses on beautification for readability. To minify, you can take the formatted output and remove whitespace, or look for a dedicated JSON minifier.

Why does my deeply nested JSON look hard to read even when formatted?+

Very deep nesting naturally produces long indentation chains regardless of formatting. Consider whether the underlying data structure could be flattened, or use a JSON viewer with collapsible tree nodes for deep objects.