Format, validate, and beautify JSON with syntax highlighting. Minify or pretty-print with 2 or 4 spaces. Free developer tool. This tool runs entirely in your browser — no data is sent to any server. It's fast, free, and works on any device.
JSON (JavaScript Object Notation) is the most common data format for APIs, configuration files, and data exchange. Raw API responses and minified JSON are nearly impossible to read — this formatter adds proper indentation and line breaks to make the structure clear. It also validates your JSON, catching syntax errors like missing commas, unmatched brackets, and invalid values with helpful error messages. Beyond formatting, the tool can minify valid JSON (remove all whitespace) for production use, reducing file size. Whether you're debugging an API response, editing a configuration file, or preparing data for a request body, properly formatted JSON saves time and prevents errors.
Common errors: trailing commas (not allowed in JSON), single quotes (must use double), unquoted keys, comments (not allowed), missing commas between items, and mismatched brackets/braces.
JSON is stricter: keys must be double-quoted strings, no trailing commas, no comments, no functions, only strings/numbers/booleans/null/arrays/objects as values. Valid JSON is valid JS, but not vice versa.
2 spaces is more common in web development and reduces file size. 4 spaces provides more visual separation. Pick one and be consistent across your project. Tabs are also valid but less common in JSON.
JSONL has one JSON object per line. This tool handles standard JSON. For JSONL, format each line separately. Many log processors and streaming APIs use JSONL format.
The tool works well with JSON up to a few MB. Very large files (50MB+) may slow the browser. For large-scale JSON processing, use command-line tools like jq or Python's json module.