How to Format and Validate JSON Online
JSON (JavaScript Object Notation) is the most common way to move data between apps and APIs. But raw JSON is often a single unreadable line, or contains a small syntax error that breaks everything. A JSON formatter beautifies the structure and instantly points out mistakes.
What is JSON?
JSON stores data as key–value pairs and lists, using curly braces for objects and square brackets for arrays. It's lightweight, human-readable when formatted, and understood by almost every programming language.
Formatting vs minifying
- Format (beautify): adds indentation and line breaks so the structure is easy to read and debug.
- Minify: removes all whitespace to make the file as small as possible for faster transfer.
Step-by-step: format your JSON
- Open the JSON Formatter.
- Paste your JSON into the input box.
- Click Format to beautify it, or Minify to compress it.
- If there's an error, the tool shows exactly what's wrong. Fix it and try again.
Common JSON errors
- Trailing commas — JSON doesn't allow a comma after the last item.
- Single quotes — keys and strings must use double quotes.
- Missing brackets — every { and [ needs a matching } and ].
- Unquoted keys — all keys must be in double quotes.
Frequently Asked Questions
Does it change my data?
No. Formatting only changes spacing and indentation; the actual values stay identical.
Why is my JSON invalid?
Usually a trailing comma, single quotes, or a missing bracket. The validator highlights the exact issue.
Is my data uploaded anywhere?
No. Parsing happens entirely in your browser, so sensitive data stays private.
Can it handle large JSON files?
Yes, within your device's memory. Very large files may take a moment to process.
Is it free?
Yes, free with no sign-up.
Try the JSON Formatter