Paste JSON and instantly validate, format (beautify) or minify it — with syntax highlighting and precise error messages showing the exact line and position. Everything runs in your browser; your data never leaves your device.
Your formatted JSON will appear here.
🔒 100% private — formatting happens locally in your browser with JavaScript. Nothing is uploaded anywhere.
JSON (JavaScript Object Notation) is the standard data format for APIs, configs and web apps. Formatting (beautifying) adds indentation and line breaks so humans can read it; minifying strips all unnecessary whitespace so it is as small as possible for sending over the network. Validating checks that the JSON follows the strict JSON rules — for example, keys must be in double quotes and trailing commas are not allowed.
Common JSON errors this tool catches
Single quotes instead of double quotes: {'a':1} → must be {"a":1}
Trailing commas:{"a":1,} → remove the last comma
Unquoted keys:{a:1} → must be {"a":1}
Comments — plain JSON does not allow // comments
Frequently asked questions
How do I format JSON online?
Paste your JSON into the box above and click Format — the tool validates it first, then pretty-prints it with indentation and syntax highlighting. If the JSON is invalid, you get the exact line and position of the error.
What is the difference between formatting and minifying JSON?
Formatting (beautifying) adds indentation and line breaks so humans can read the JSON. Minifying removes all unnecessary whitespace so the JSON is as small as possible for sending over the network. Both represent the same data.
Is my JSON data safe here?
Yes. Everything runs locally in your browser with JavaScript — your JSON is never uploaded to any server.
Is this JSON formatter free?
Yes. It is 100% free with no signup required.
What are the most common JSON errors?
Trailing commas before } or ], single quotes instead of double quotes, unquoted keys, comments (// or /* */), and stray control characters. This formatter flags each one with its exact line and position so you can fix it in seconds.
Is minified JSON still valid JSON?
Yes — completely. Whitespace outside strings is insignificant in JSON, so the minified and pretty versions are byte-different but data-identical. Minify for sending over the network; pretty-print for reading and debugging.
Can JSON contain comments?
No — the JSON specification has no comments, and strict parsers reject them. The common workaround is a dummy field like "_comment": "explanation", which parsers simply treat as data.
How JSON validation and formatting works
JSON has strict grammar: keys and strings need double quotes (never single), no trailing commas, no comments, and values must be strings, numbers, booleans, null, arrays, or objects. The formatter first parses your text against these rules — if it fails, you get the exact line and character of the error instead of a cryptic crash. If it passes, it pretty-prints (adds indentation and line breaks for humans) or minifies (strips all unnecessary whitespace for machines). Both outputs represent identical data.
Worked example: catching a trailing comma
You paste {"name": "Ali", "age": 30,}. The parser stops at the comma after 30 — position 24 — because JSON forbids a comma before a closing brace. Remove it: {"name": "Ali", "age": 30} validates cleanly. Pretty-printed, that becomes three readable lines; minified, it stays one compact line. Same data, two presentations.
Practical tips
Always validate API responses before pasting them into code — one stray comma breaks the whole parse. Minify only what you send over the network; keep the pretty version for debugging. And remember JSON has no date type — dates travel as strings like "2026-10-19", so agree on the format with whoever consumes your data.
JSON is not a JavaScript object
They look alike, but JSON is stricter: keys must be double-quoted ({name: "Ali"} is valid JavaScript but invalid JSON), no functions, no undefined, no trailing commas, and no comments. This trips up developers daily — code that runs fine in the browser explodes the moment it is stringified or sent to an API. The formatter enforces the strict subset, which is why pasting a JS object literal here often surfaces the exact spot where it stops being JSON. When in doubt, remember: JSON is a data interchange format wearing JavaScript's clothes, and it dresses more formally than its cousin.
Key takeaways
JSON demands double quotes, no trailing commas, no comments — stricter than JavaScript objects.
Validate first (the error position tells you exactly what broke), then pretty-print for humans or minify for machines.
Minified and pretty JSON are data-identical; whitespace is insignificant.