Formatted JSON will appear here after validation…
Paste any JSON and instantly validate its syntax, format it for readability, or minify it for production. Clear error messages tell you exactly what's wrong and how to fix it.
A JSON validator reads your JSON string and checks it against the JSON specification (RFC 8259) to confirm it's syntactically correct. Beyond just saying "valid" or "invalid," a good validator tells you exactly which line has the problem and gives you a hint about what went wrong.
JSON (JavaScript Object Notation) looks simple, but it has strict rules that catch developers off guard — especially if you're coming from JavaScript where unquoted keys and trailing commas are allowed. One missing quote, one extra comma, or one stray comment can break an entire API payload.
This tool validates the syntax, pretty-prints the structure for easy reading, minifies it for production payloads, and calculates stats like total key count and nesting depth — all in one click.
JSON has only a handful of rules, but breaking any one of them silently kills your API call or config file.
These are the errors this tool catches most often — and the ones that burn the most debugging time.
{name: "Alice"} instead of {"name": "Alice"}. Object keys must always be double-quoted strings. This is valid JavaScript but invalid JSON.{'key': 'value'}. JSON only accepts double quotes. Replace every single quote around strings with a double quote.{"a": 1, "b": 2,} — the comma after 2 is invalid. Remove the last comma from any array or object.{ vs } and [ vs ] — they must balance.{"port": 3000 // default} — comments of any form are invalid in JSON. Remove all // and /* */ lines before validating.{"count": undefined} or {"ratio": NaN} — these JavaScript primitives do not exist in JSON. Use null instead.\n, \t, and \r escape sequences instead.{"id": 1, "id": 2} — duplicate keys are technically parseable but lead to unpredictable results. Different parsers handle them differently. Always use unique keys.JSON supports exactly six value types. Understanding each one prevents a whole class of validation errors.
JSON is the default choice for most APIs, but understanding how it compares helps you pick the right format for your use case.
| JSON | XML | YAML | |
|---|---|---|---|
| Human readable | ✅ Easy | ⚠️ Verbose | ✅ Very easy |
| Comment support | ❌ None | ✅ Yes | ✅ Yes |
| Data types | 6 built-in | Strings only | Rich types |
| File size | ✅ Compact | ❌ Verbose | ✅ Compact |
| Parser availability | ✅ Native | ⚠️ Library | ⚠️ Library |
| Best for | APIs & config | Documents & SOAP | Config files |
const obj = {} will often fail JSON validation.JSON.parse() uses IEEE 754 double-precision floats, which lose precision for integers larger than 2^53. If you're working with large IDs or financial values, encode them as strings or use a BigInt-aware parser.Check your website's technical health with our full suite of free SEO and web tools.
