Free JSON Formatter & Validator

How this tool computes its result

Validates JSON via JSON.parse(), capturing syntax errors with position information and converting to line/column numbers for user-facing error reporting. Formatting beautifies by parsing and re-stringifying with a specified indent (2, 4, 1, or 0 spaces). Minification re-stringifies with no indent (indent 0). Stats panel reports line count, character count, and byte size via Blob. All operations are client-side with no network calls.

Worked example

Pasting {"name":"test","value":123} with 2-space indent produces formatted output with each key-value pair on its own line with 2-space indentation. Minifying the same produces {"name":"test","value":123} (identical in this case, but on a single line for a multi-object structure). Invalid JSON like {"name":"test",} shows error "Unexpected token }" with line/column number.

When not to use this tool

This handles JSON structure only - it does not validate the semantic meaning of your data (e.g., no check that required fields are present), does not sort keys or normalize order, and does not support JSON5 or other extensions; for those, use a specialized JSON validator or code editor with plugins.

Common mistakes

• - Pasting JSON with a trailing comma ({"a":1,}) expecting auto-fix - the tool rejects it as invalid; JSON does not allow trailing commas, and this tool does not auto-repair syntax errors.
• - Expecting minify to produce smaller output - minified JSON is always single-line and removes whitespace, but the actual byte count may not be smaller unless there is significant indentation in the original; minify is useful for transmission, not always for storage shrinkage.
• - Assuming "format with 4-space indent" will match your project's code style - the tool offers preset indents only; if your project uses custom indentation or tab characters, format the JSON, then manually adjust in your editor.

Related tools