JSON runs the modern web — APIs, config files, data exports — but in the wild it usually arrives as one crushed, unreadable line, or worse, as a broken payload with an error hiding in thousands of characters. This formatter does both jobs developers need dozens of times a week: paste in compact or messy JSON and it reprints it with clean, consistent indentation you can actually read; and when the JSON is invalid, it tells you so and reports where the parser failed, instead of leaving you to hunt for a missing comma by eye. You can also minify valid JSON back down for production use. Everything parses locally in your browser, so payloads containing tokens or customer data never touch a server.
Quick Answer: Paste JSON to format it with clean indentation, validate it, or minify it — and if it is broken, see the error and its position instantly.
Free Online Tool
JSON Formatter & Validator
Crushed or broken JSON in — clean, checked JSON out.
How to Use the JSON Formatter & Validator
- Paste your JSON into the input box — one line or a whole file, it does not matter.
- Press Format to pretty-print it with two-space indentation.
- If the JSON is invalid, read the error message and position to find the fault.
- Use Minify when you need the compact version back for a config or payload.
- Copy the result, or download it as a .json file.
Key Features
- Pretty-printing with consistent two-space indentation.
- Real validation with the parser’s own error message and character position.
- One-click minify for production payloads and configs.
- Live size readout: characters before and after formatting.
- Parses entirely in your browser — safe for payloads with secrets.
Best Practices and Tips
- JSON allows no trailing commas and requires double quotes around keys — the two most common causes of ‘invalid JSON’ are exactly those.
- When an API returns an error, format the response body first; nested error objects are much easier to spot indented.
- Keep a formatted copy of production configs in version control; the diff between two formatted files is readable, between two minified ones is not.
- Numbers in JSON cannot have leading zeros and strings must escape backslashes — the validator will catch both.
- Use the character position in the error to jump straight to the neighbourhood of the problem in your editor.
Common Mistakes to Avoid
- Pasting JSON with single-quoted strings (that is JavaScript object syntax, not JSON) and expecting it to validate.
- Including comments in JSON — the format has none, and any // or /* */ will break parsing.
- Assuming a formatted result means a correct structure; formatting validates syntax, not whether the fields make sense for your API.
- Sending sensitive payloads to online formatters generally — this one runs locally, but the habit is worth keeping everywhere.
Frequently Asked Questions
What does the error position mean?
When parsing fails, the browser’s JSON parser reports a position in the text near where it gave up. The fault is usually at or just before that point — a missing comma at the end of the previous line is the classic culprit.
What is the difference between formatting and validating?
Validating answers ‘is this legal JSON?’. Formatting assumes it is (or tells you it is not) and then rewrites it with consistent line breaks and indentation so humans can read the structure. This tool always validates as part of formatting.
Can it handle very large JSON files?
Yes — megabyte-sized payloads format comfortably in a modern browser. Extremely large files (tens of megabytes) may take a few seconds, but nothing is uploaded, so the wait is only your own machine working.
Why does my JSON have \u escapes or slashes everywhere?
Some exporters escape forward slashes and non-ASCII characters. The data is still valid; formatting will display it in readable structure, and most parsers accept the escapes as-is when you use the data again.
Does minifying change the data?
No. Minify removes only whitespace between tokens; keys, values, order and nesting are identical. Any compliant parser produces the same object from the minified and formatted versions.
Related Tools
- YAML to JSON Converter – parses YAML properly and outputs clean, formatted JSON
- JSON to XML Converter – transforms JSON structures into properly escaped, indented XML
- CSV to JSON Converter – turns CSV rows into a clean JSON array using your headers
- JWT Decoder – decodes JWT headers and payloads into readable JSON, locally